Oracle® Database Express Edition

2 Day Developer's Guide

11g Release 2 (11.2)

E18147-13

March 2014

Oracle Database Express Edition 2 Day Developer's Guide, 11g Release 2 (11.2)

E18147-13

Copyright © 2005, 2014, Oracle and/or its affiliates. All rights reserved.

Primary Author:  Sheila Moore

Contributors: Eric Belden, Bjorn Engsig, Nancy Greenberg, Pat Huey, Christopher Jones, Sharon Kennedy, Simon Law, Roza Leyderman, Bryn Llewellen, Chuck Murray, Mark Townsend

This software and related documentation are provided under a license agreement containing restrictions on use and disclosure and are protected by intellectual property laws. Except as expressly permitted in your license agreement or allowed by law, you may not use, copy, reproduce, translate, broadcast, modify, license, transmit, distribute, exhibit, perform, publish, or display any part, in any form, or by any means. Reverse engineering, disassembly, or decompilation of this software, unless required by law for interoperability, is prohibited.

The information contained herein is subject to change without notice and is not warranted to be error-free. If you find any errors, please report them to us in writing.

If this is software or related documentation that is delivered to the U.S. Government or anyone licensing it on behalf of the U.S. Government, the following notice is applicable:

U.S. GOVERNMENT END USERS: Oracle programs, including any operating system, integrated software, any programs installed on the hardware, and/or documentation, delivered to U.S. Government end users are "commercial computer software" pursuant to the applicable Federal Acquisition Regulation and agency-specific supplemental regulations. As such, use, duplication, disclosure, modification, and adaptation of the programs, including any operating system, integrated software, any programs installed on the hardware, and/or documentation, shall be subject to license terms and license restrictions applicable to the programs. No other rights are granted to the U.S. Government.

This software or hardware is developed for general use in a variety of information management applications. It is not developed or intended for use in any inherently dangerous applications, including applications that may create a risk of personal injury. If you use this software or hardware in dangerous applications, then you shall be responsible to take all appropriate fail-safe, backup, redundancy, and other measures to ensure its safe use. Oracle Corporation and its affiliates disclaim any liability for any damages caused by use of this software or hardware in dangerous applications.

Oracle and Java are registered trademarks of Oracle and/or its affiliates. Other names may be trademarks of their respective owners.

Intel and Intel Xeon are trademarks or registered trademarks of Intel Corporation. All SPARC trademarks are used under license and are trademarks or registered trademarks of SPARC International, Inc. AMD, Opteron, the AMD logo, and the AMD Opteron logo are trademarks or registered trademarks of Advanced Micro Devices. UNIX is a registered trademark of The Open Group.

This software or hardware and documentation may provide access to or information on content, products, and services from third parties. Oracle Corporation and its affiliates are not responsible for and expressly disclaim all warranties of any kind with respect to third-party content, products, and services. Oracle Corporation and its affiliates will not be responsible for any loss, costs, or damages incurred due to your access to or use of third-party content, products, or services.

Contents

List of Examples

List of Tables

Preface

- Audience

- Documentation Accessibility

- Related Documents

- Conventions

Changes in This Release for Oracle Database Express Edition 2 Day Developer's Guide

- Changes in Oracle Database 11g Release 2 (11.2.0.2)

1 Introduction

- About Oracle Database Express Edition Developers

- About This Document

- About Oracle Database Express Edition

- About Schema Objects

- About Oracle Database Express Edition Access

- About SQL*Plus

- About SQL Developer

- About Structured Query Language (SQL)

- About Procedural Language/SQL (PL/SQL)

- About Other Client Programs, Languages, and Development Tools

- About Sample Schema HR

2 Connecting to Oracle Database Express Edition and Exploring It

- Connecting to Oracle Database Express Edition from SQL*Plus

- Connecting to Oracle Database Express Edition from SQL Developer

- Connecting to Oracle Database Express Edition as User HR

- Unlocking the HR Account

- Connecting to Oracle Database Express Edition as User HR from SQL*Plus

- Connecting to Oracle Database Express Edition as User HR from SQL Developer

- Exploring Oracle Database Express Edition with SQL*Plus

- Viewing HR Schema Objects with SQL*Plus

- Viewing EMPLOYEES Table Properties and Data with SQL*Plus

- Exploring Oracle Database Express Edition with SQL Developer

- Tutorial: Viewing HR Schema Objects with SQL Developer

- Tutorial: Viewing EMPLOYEES Table Properties and Data with SQL Developer

- Selecting Table Data

- About Queries

- Running Queries in SQL Developer

- Tutorial: Selecting All Columns of a Table

- Tutorial: Selecting Specific Columns of a Table

- Displaying Selected Columns Under New Headings

- Selecting Data that Satisfies Specified Conditions

- Sorting Selected Data

- Selecting Data from Multiple Tables

- Using Operators and Functions in Queries

- Using Arithmetic Operators in Queries

- Using Numeric Functions in Queries

- Using the Concatenation Operator in Queries

- Using Character Functions in Queries

- Using Datetime Functions in Queries

- Using Conversion Functions in Queries

- Using Aggregate Functions in Queries

- Using NULL-Related Functions in Queries

- Using CASE Expressions in Queries

- Using the DECODE Function in Queries

3 About DML Statements and Transactions

- About Data Manipulation Language (DML) Statements

- About the INSERT Statement

- About the UPDATE Statement

- About the DELETE Statement

- About Transaction Control Statements

- Committing Transactions

- Rolling Back Transactions

- Setting Savepoints in Transactions

4 Creating and Managing Schema Objects

- About Data Definition Language (DDL) Statements

- Creating and Managing Tables

- About SQL Data Types

- Creating Tables

- Tutorial: Creating a Table with the Create Table Tool

- Creating Tables with the CREATE TABLE Statement

- Ensuring Data Integrity in Tables

- About Constraint Types

- Tutorial: Adding Constraints to Existing Tables

- Tutorial: Adding Rows to Tables with the Insert Row Tool

- Tutorial: Changing Data in Tables in the Data Pane

- Tutorial: Deleting Rows from Tables with the Delete Selected Row(s) Tool

- Managing Indexes

- Tutorial: Adding an Index with the Create Index Tool

- Tutorial: Changing an Index with the Edit Index Tool

- Tutorial: Dropping an Index

- Dropping Tables

- Creating and Managing Views

- Creating Views

- Tutorial: Creating a View with the Create View Tool

- Creating Views with the CREATE VIEW Statement

- Changing Queries in Views

- Tutorial: Changing View Names with the Rename Tool

- Dropping Views

- Creating and Managing Sequences

- Tutorial: Creating a Sequence

- Dropping Sequences

- Creating and Managing Synonyms

- Creating Synonyms

- Dropping Synonyms

5 Developing Stored Subprograms and Packages

- About Stored Subprograms

- About Packages

- About PL/SQL Identifiers

- About PL/SQL Data Types

- Creating and Managing Standalone Subprograms

- About Subprogram Structure

- Tutorial: Creating a Standalone Procedure

- Tutorial: Creating a Standalone Function

- Changing Standalone Subprograms

- Tutorial: Testing a Standalone Function

- Dropping Standalone Subprograms

- Creating and Managing Packages

- About Package Structure

- Tutorial: Creating a Package Specification

- Tutorial: Changing a Package Specification

- Tutorial: Creating a Package Body

- Dropping a Package

- Declaring and Assigning Values to Variables and Constants

- Tutorial: Declaring Variables and Constants in a Subprogram

- Ensuring that Variables, Constants, and Parameters Have Correct Data Types

- Tutorial: Changing Declarations to Use the %TYPE Attribute

- Assigning Values to Variables

- Assigning Values to Variables with the Assignment Operator

- Assigning Values to Variables with the SELECT INTO Statement

- Controlling Program Flow

- About Control Statements

- Using the IF Statement

- Using the CASE Statement

- Using the FOR LOOP Statement

- Using the WHILE LOOP Statement

- Using the Basic LOOP and EXIT WHEN Statements

- Using Records and Cursors

- About Records

- Tutorial: Declaring a RECORD Type

- Tutorial: Creating and Invoking a Subprogram with a Record Parameter

- About Cursors

- Using a Declared Cursor to Retrieve Result Set Rows One at a Time

- Tutorial: Using a Declared Cursor to Retrieve Result Set Rows One at a Time

- About Cursor Variables

- Using a Cursor Variable to Retrieve Result Set Rows One at a Time

- Tutorial: Using a Cursor Variable to Retrieve Result Set Rows One at a Time

- Using Associative Arrays

- About Collections

- About Associative Arrays

- Declaring Associative Arrays

- Populating Associative Arrays

- Traversing Dense Associative Arrays

- Traversing Sparse Associative Arrays

- Handling Exceptions (Runtime Errors)

- About Exceptions and Exception Handlers

- When to Use Exception Handlers

- Handling Predefined Exceptions

- Declaring and Handling User-Defined Exceptions

6 Using Triggers

- About Triggers

- Creating Triggers

- About OLD and NEW Pseudorecords

- Tutorial: Creating a Trigger that Logs Table Changes

- Tutorial: Creating a Trigger that Generates a Primary Key for a Row Before It Is Inserted

- Creating an INSTEAD OF Trigger

- Tutorial: Creating Triggers that Log LOGON and LOGOFF Events

- Changing Triggers

- Disabling and Enabling Triggers

- Disabling or Enabling a Single Trigger

- Disabling or Enabling All Triggers on a Single Table

- About Trigger Compilation and Dependencies

- Dropping Triggers

7 Working in a Global Environment

- About Globalization Support Features

- About Language Support

- About Territory Support

- About Date and Time Formats

- About Calendar Formats

- About Numeric and Monetary Formats

- About Linguistic Sorting and String Searching

- About Length Semantics

- About Unicode and SQL National Character Data Types

- About Initial NLS Parameter Values

- Viewing NLS Parameter Values

- Changing NLS Parameter Values

- Changing NLS Parameter Values for All SQL Developer Connections

- Changing NLS Parameter Values for the Current SQL Function Invocation

- About Individual NLS Parameters

- About Locale and the NLS_LANG Parameter

- About the NLS_LANGUAGE Parameter

- About the NLS_TERRITORY Parameter

- About the NLS_DATE_FORMAT Parameter

- About the NLS_DATE_LANGUAGE Parameter

- About NLS_TIMESTAMP_FORMAT and NLS_TIMESTAMP_TZ_FORMAT Parameters

- About the NLS_CALENDAR Parameter

- About the NLS_NUMERIC_CHARACTERS Parameter

- About the NLS_CURRENCY Parameter

- About the NLS_ISO_CURRENCY Parameter

- About the NLS_DUAL_CURRENCY Parameter

- About the NLS_SORT Parameter

- About the NLS_COMP Parameter

- About the NLS_LENGTH_SEMANTICS Parameter

- Using Unicode in Globalized Applications

- Representing Unicode String Literals in SQL and PL/SQL

- Avoiding Data Loss During Character-Set Conversion

8 Building Effective Applications

- Building Scalable Applications

- About Scalable Applications

- Using Bind Arguments to Improve Scalability

- Using PL/SQL to Improve Scalability

- How PL/SQL Minimizes Parsing

- About the EXECUTE IMMEDIATE Statement

- About OPEN FOR Statements

- About the DBMS_SQL Package

- About Bulk SQL

- About Concurrency and Scalability

- About Sequences and Concurrency

- About Latches and Concurrency

- About Nonblocking Reads and Writes and Concurrency

- About Shared SQL and Concurrency

- Limiting the Number of Concurrent Sessions

- Comparing Programming Techniques with Runstats

- About Runstats

- Setting Up Runstats

- Using Runstats

- Recommended Programming Practices

- Use Instrumentation Packages

- Statistics Gathering and Application Tracing

- Use Existing Functionality

- Cover Database Tables with Editioning Views

- Recommended Security Practices

9 Developing a Simple Oracle Database Express Edition Application

- About the Application

- Purpose of the Application

- Structure of the Application

- Schema Objects of the Application

- Schemas for the Application

- Naming Conventions in the Application

- Creating the Schemas for the Application

- Granting Privileges to the Schemas

- Granting Privileges to the app_data Schema

- Granting Privileges to the app_code Schema

- Granting Privileges to the app_admin Schema

- Granting Privileges to the app_user and app_admin_user Schemas

- Creating the Schema Objects and Loading the Data

- Creating the Tables

- Creating the Editioning Views

- Creating the Triggers

- Creating the Trigger to Enforce the First Business Rule

- Creating the Trigger to Enforce the Second Business Rule

- Creating the Sequences

- Loading the Data

- Adding the Foreign Key Constraint

- Granting Privileges on the Schema Objects to Users

- Creating the employees_pkg Package

- Creating the Package Specification for employees_pkg

- Creating the Package Body for employees_pkg

- Tutorial: Showing How the employees_pkg Subprograms Work

- Granting the Execute Privilege to app_user and app_user_admin

- Tutorial: Invoking get_job_history as app_user or app_admin_user

- Creating the admin_pkg Package

- Creating the Package Specification for admin_pkg

- Creating the Package Body for admin_pkg

- Tutorial: Showing How the admin_pkg Subprograms Work

- Granting the Execute Privilege to app_user_admin

- Tutorial: Invoking add_department as app_admin_user

10 Deploying an Oracle Database Express Edition Application

- About Development and Deployment Environments

- About Installation Scripts

- About DDL Statements and Schema Object Dependencies

- About INSERT Statements and Constraints

- Creating Installation Scripts

- Creating Installation Scripts with the Cart

- Creating an Installation Script with the Database Export Wizard

- Editing Installation Scripts that Create Sequences

- Editing Installation Scripts that Create Triggers

- Creating Installation Scripts for the Sample Application

- Creating Installation Script schemas.sql

- Creating Installation Script objects.sql

- Creating Installation Script employees.sql

- Creating Installation Script admin.sql

- Creating Master Installation Script create_app.sql

- Deploying the Sample Application

- Checking the Validity of an Installation

- Archiving the Installation Scripts

Index

List of Examples

- 2-1 Connecting to Oracle Database from SQL*Plus

- 2-2 Viewing HR Schema Objects with SQL*Plus

- 2-3 Viewing EMPLOYEES Table Properties with SQL*Plus

- 2-4 Viewing EMPLOYEES Table Data with SQL*Plus

- 2-5 Displaying Selected Columns Under New Headings

- 2-6 Preserving Case and Including Spaces in Column Aliases

- 2-7 Selecting Data from One Department

- 2-8 Selecting Data for Last Names that Start with the Same Substring

- 2-9 Selecting Data that Satisfies Two Conditions

- 2-10 Sorting Selected Data by LAST_NAME

- 2-11 Sorting Selected Data by an Unselected Column

- 2-12 Selecting Data from Two Tables (Joining Two Tables)

- 2-13 Using an Arithmetic Expression in a Query

- 2-14 Rounding Numeric Data

- 2-15 Truncating Numeric Data

- 2-16 Concatenating Character Data

- 2-17 Changing the Case of Character Data

- 2-18 Displaying the Number of Years Between Dates

- 2-19 Displaying System Date and Time

- 2-20 Converting Dates to Characters Using a Format Template

- 2-21 Converting Characters to Numbers

- 2-22 Counting the Number of Rows in Each Group

- 2-23 Limiting Aggregate Functions to Rows that Satisfy a Condition

- 2-24 Using Aggregate Functions for Statistical Information

- 2-25 Substituting a String for a NULL Value

- 2-26 Specifying Different Expressions for NULL and Not NULL Values

- 2-27 Using a Simple CASE Expression in a Query

- 2-28 Using a Searched CASE Expression in a Query

- 2-29 Using the DECODE Function in a Query

- 3-1 Using the INSERT Statement When All Information Is Available

- 3-2 Using the INSERT Statement When Not All Information Is Available

- 3-3 Using the INSERT Statement Incorrectly

- 3-4 Using the UPDATE Statement to Add Data

- 3-5 Using the UPDATE Statement to Update Multiple Rows

- 3-6 Using the DELETE Statement

- 3-7 Committing a Transaction

- 3-8 Rolling Back an Entire Transaction

- 3-9 Rolling Back a Transaction to a Savepoint

- 4-1 Creating the EVALUATIONS Table with CREATE TABLE

- 4-2 Creating the SCORES Table with CREATE TABLE

- 4-3 Creating the EMP_LOCATIONS View with CREATE VIEW

- 4-4 Changing the Query in the SALESFORCE View

- 5-1 Assigning Values to a Variable with Assignment Operator

- 5-2 Assigning Table Values to Variables with SELECT INTO

- 5-3 Inserting a Table Row with Values from Another Table

- 5-4 IF Statement that Determines Return Value of Function

- 5-5 CASE Statement that Determines Which String to Print

- 5-6 FOR LOOP Statement that Computes Salary After Five Years

- 5-7 WHILE LOOP Statement that Computes Salary to Maximum

- 5-8 Using the EXIT WHEN Statement

- 5-9 Declaring Associative Arrays

- 5-10 Populating Associative Arrays

- 5-11 Traversing a Dense Associative Array

- 5-12 Traversing a Sparse Associative Array

- 5-13 Handling Predefined Exception NO_DATA_FOUND

- 5-14 Handling User-Defined Exceptions

- 6-1 Creating an INSTEAD OF Trigger

- 7-1 NLS_LANGUAGE Affects Server Message and Month Abbreviations

- 7-2 NLS_TERRITORY Affects Currency Symbol

- 7-3 NLS_TERRITORY Affects Date Formats

- 7-4 NLS_DATE_FORMAT Overrides NLS_TERRITORY

- 7-5 NLS_DATE_LANGUAGE Affects Displayed SYSDATE

- 7-6 NLS_CALENDAR Affects Displayed SYSDATE

- 7-7 NLS_NUMERIC_CHARACTERS Affects Decimal Character and Group Separator

- 7-8 NLS_CURRENCY Overrides NLS_TERRITORY

- 7-9 NLS_ISO_CURRENCY

- 7-10 NLS_SORT Affects Linguistic Sort Order

- 7-11 NLS_COMP Affects SQL Character Comparison

- 7-12 NLS_LENGTH_SEMANTICS Affects Storage of VARCHAR2 Column

- 8-1 Bind Variable Improves Performance

- 8-2 Bulk SQL

- 8-3 Without Bulk SQL

- 8-4 Concurrent Dequeuing Transactions

List of Tables

- 5-1 Cursor Attribute Values

- 7-1 Initial Values of NLS Parameters in SQL Developer

Preface

This document explains basic concepts behind application development with Oracle Database Express Edition. It provides instructions for using the basic features of topics through Structured Query Language (SQL), and the Oracle server-based procedural extension to the SQL database language, Procedural Language/Structured Query Language (PL/SQL).

This preface contains:

- Audience

- Documentation Accessibility

- Related Documents

- Conventions

Audience

This document is intended for anyone who wants to learn about Oracle Database Express Edition application development, and is primarily an introduction to application development for developers who are new to Oracle Database Express Edition.

This document assumes that you have a general understanding of relational database concepts and an understanding of the operating system environment that you will use to develop applications with Oracle Database Express Edition.

Documentation Accessibility

For information about Oracle's commitment to accessibility, visit the Oracle Accessibility Program website at http://www.oracle.com/pls/topic/lookup?ctx=acc&id=docacc.

Access to Oracle Support

Oracle customers have access to electronic support through My Oracle Support. For information, visit http://www.oracle.com/pls/topic/lookup?ctx=acc&id=info or visit http://www.oracle.com/pls/topic/lookup?ctx=acc&id=trs if you are hearing impaired.

Related Documents

As you become comfortable with the concepts and tasks in this document, Oracle recommends that you consult other Oracle Database Express Edition development documents, especially:

- Oracle Database Express Edition 2 Day + Application Express Developer's Guide

- Oracle Database Express Edition 2 Day + Java Developer's Guide

- Oracle Database Express Edition 2 Day + .NET Developer's Guide for Microsoft Windows

- Oracle Database Express Edition 2 Day + PHP Developer's Guide

For more information, see:

- Oracle Database Concepts

- Oracle Database Advanced Application Developer's Guide

- Oracle Database SQL Language Reference

- Oracle Database PL/SQL Language Reference

Conventions

This document uses these text conventions:

Convention

Meaning

boldface

Boldface type indicates graphical user interface elements associated with an action, or terms defined in text or the glossary.

italic

Italic type indicates book titles, emphasis, or placeholder variables for which you supply particular values.

monospace

Monospace type indicates commands within a paragraph, URLs, code in examples, text that appears on the screen, or text that you enter.

Changes in This Release for Oracle Database Express Edition 2 Day Developer's Guide

This preface contains:

- Changes in Oracle Database 11g Release 2 (11.2.0.2)

Changes in Oracle Database 11g Release 2 (11.2.0.2)

For Oracle Database 11g Release 2 (11.2.0.2), Oracle Database Express Edition 2 Day Developer's Guide has these changes:

- If you use SQL Developer, Oracle recommends using version 4.0 or later (see "Connecting to Oracle Database Express Edition from SQL Developer").

- Chapter 2, "Connecting to Oracle Database Express Edition and Exploring It," covers the topics previously covered in Chapter 1 through Chapter 3, has the new topic "Exploring Oracle Database Express Edition with SQL*Plus", and has some new and changed examples.

- The schema objects that you create in the tutorials in Chapter 3, "About DML Statements and Transactions," Chapter 4, "Creating and Managing Schema Objects," and Chapter 5, "Developing Stored Subprograms and Packages," (formerly Chapter 5, Chapter 6, and Chapter 7) are no longer used in a sample application.

- Chapter 5, "Developing Stored Subprograms and Packages," has the new topic "When to Use Exception Handlers".

- New Chapter 8, "Building Effective Applications," explains how to build scalable applications and use recommended programming and security practices.

- New Chapter 9, "Developing a Simple Oracle Database Express Edition Application," shows how to develop a simple Oracle Database Express Edition application.

- Chapter 10, "Deploying an Oracle Database Express Edition Application," has the new topic "Creating Installation Scripts with the Cart" and explains how to deploy the application that you develop in Chapter 9.

1 Introduction

This chapter contains:

- About Oracle Database Express Edition Developers

- About This Document

- About Oracle Database Express Edition

- About Sample Schema HR

About Oracle Database Express Edition Developers

An Oracle Database Express Edition developer is responsible for creating or maintaining the database components of an application that uses the Oracle technology stack. Oracle Database Express Edition developers either develop applications or convert existing applications to run in the Oracle Database Express Edition environment.

See Also:
Oracle Database Concepts for more information about the duties of Oracle Database developers

About This Document

This document is the entry into the Oracle Database Express Edition documentation set for application developers. It does the following:

- Explains the basic concepts behind development with Oracle Database Express Edition

- Shows, with tutorials and examples, how to use basic features of SQL and PL/SQL

- Provides references to detailed information about subjects that it introduces

- Shows how to develop and deploy a simple Oracle Database Express Edition application

Chapter 1, "Introduction," describes the reader for whom this document is intended, outlines the organization of this document, introduces important Oracle Database Express Edition concepts, and describes the sample schema used in the tutorials and examples in this document.

Chapter 2, "Connecting to Oracle Database Express Edition and Exploring It," explains how to connect to Oracle Database Express Edition, how to view schema objects and the properties and data of Oracle Database Express Edition tables, and how to use queries to retrieve data from an Oracle Database Express Edition table.

Chapter 3, "About DML Statements and Transactions," introduces data manipulation language (DML) statements and transactions. DML statements add, change, and delete Oracle Database Express Edition table data. A transaction is a sequence of one or more SQL statements that Oracle Database Express Edition treats as a unit: either all of the statements are performed, or none of them are.

Chapter 4, "Creating and Managing Schema Objects," introduces data definition language (DDL) statements, which create, change, and drop schema objects.

Chapter 5, "Developing Stored Subprograms and Packages," introduces stored subprograms and packages, which can be used as building blocks for many different database applications.

Chapter 6, "Using Triggers," introduces triggers, which are stored PL/SQL units that automatically execute ("fire") in response to specified events.

Chapter 7, "Working in a Global Environment," introduces globalization support—National Language Support (NLS) parameters and Unicode-related features of SQL and PL/SQL.

Chapter 8, "Building Effective Applications," explains how to build scalable applications and use recommended programming and security practices.

Chapter 9, "Developing a Simple Oracle Database Express Edition Application," shows how to develop a simple Oracle Database Express Edition application.

Chapter 10, "Deploying an Oracle Database Express Edition Application," explains how to deploy an Oracle Database Express Edition application—that is, how to install it in one or more environments where other users can run it—using the application developed in Chapter 9 as an example.

About Oracle Database Express Edition

Oracle Database Express Edition groups related information into logical structures called schemas. The logical structures are called schema objects. When you connect to the database by providing your user name and password, you specify the schema and indicate that you are its owner. In Oracle Database Express Edition, the user name and the name of the schema to which the user connects are the same.

This section contains:

- About Schema Objects

- About Oracle Database Express Edition Access

About Schema Objects

Every object in an Oracle Database Express Edition belongs to only one schema, and has a unique name with that schema.

Some of the objects that schemas can contain are:

- Tables
Tables are the basic units of data storage in Oracle Database Express Edition. Tables hold all user-accessible data. Each table contains rows that represent individual data records. Rows are composed of columns that represent the fields of the records. For more information, see "Creating and Managing Tables".

- Indexes
Indexes are optional objects that can improve the performance of data retrieval from tables. Indexes are created on one or more columns of a table, and are automatically maintained in the database. For more information, see "Managing Indexes".

- Views
You can create a view that combines information from several different tables into a single presentation. A view can rely on information from both tables and other views. For more information, see "Creating and Managing Views".

- Sequences
When all records of a table must be distinct, you can use a sequence to generate a serial list of unique integers for numeric columns, each of which represents the ID of one record. For more information, see "Creating and Managing Sequences".

- Synonyms
Synonyms are aliases for schema objects. You can use synonyms for security and convenience; for example, to hide the ownership of an object or to simplify SQL statements. For more information, see "Creating and Managing Synonyms".

- Stored subprograms
Stored subprograms (also called schema-level subprograms) are procedures and functions that are stored in the database. They can be invoked from client applications that access the database. For more information, see "Developing Stored Subprograms and Packages".

Triggers are stored subprograms that are automatically run by the database when specified events occur in a particular table or view. Triggers can restrict access to specific data and perform logging. For more information, see "Using Triggers".

- Packages
A package is a group of related subprograms, along with the explicit cursors and variables they use, stored in the database as a unit, for continued use. Like stored subprograms, package subprograms can be invoked from client applications that access the database. For more information, see "Developing Stored Subprograms and Packages".

Typically, the objects that an application uses belong to the same schema.

See Also:
Oracle Database Concepts for a comprehensive introduction to schema objects

About Oracle Database Express Edition Access

You can access Oracle Database Express Edition only through a client program, such as SQL*Plus or SQL Developer. The client program's interface to Oracle Database Express Edition is Structured Query Language (SQL). Oracle provides an extension to SQL called Procedural Language/SQL (PL/SQL).

This section contains:

- About SQL*Plus

- About SQL Developer

- About Structured Query Language (SQL)

- About Procedural Language/SQL (PL/SQL)

- About Other Client Programs, Languages, and Development Tools

About SQL*Plus

SQL*Plus (pronounced sequel plus) is an interactive and batch query tool that is installed with every Oracle Database Express Edition installation. It has a command-line user interface that acts as the client when connecting to the database.

SQL*Plus has its own commands and environment. In the SQL*Plus environment, you can enter and run SQL*Plus commands, SQL statements, PL/SQL statements, and operating system commands to perform tasks such as:

- Formatting, performing calculations on, storing, and printing query results

- Examining tables and object definitions

- Developing and running batch scripts

- Performing database administration

You can use SQL*Plus to generate reports interactively, to generate reports as batch processes, and to output the results to text file, to screen, or to HTML file for browsing on the Internet. You can generate reports dynamically using the HTML output facility.

You can use SQL*Plus in SQL Developer. For details, see Oracle SQL Developer User's Guide.

See Also:

- "Connecting to Oracle Database Express Edition from SQL*Plus"

- SQL*Plus User's Guide and Reference for complete information about SQL*Plus

About SQL Developer

SQL Developer (pronounced sequel developer) is a graphic version of SQL*Plus, written in Java, that is available in the default installation of Oracle Database Express Edition and by free download.

The SQL Developer user interface includes a Connections frame, tools (with menus), and a Worksheet. From the Worksheet, you can enter and run SQL statements, PL/SQL statements, and SQL*Plus commands. You can do some tasks—for example, creating a table—either in the Worksheet or with the Connections frame and tools.

To see the name and keyboard equivalent of any SQL Developer icon, position your cursor over the icon.

Note:
SQL Developer often offers several ways to do the same task. This document does not explain every possible way to do a task with SQL Developer.

See Also:

- "Connecting to Oracle Database Express Edition from SQL Developer"

- Oracle SQL Developer User's Guide for complete information about SQL Developer

About Structured Query Language (SQL)

Structured Query Language (SQL) (pronounced sequel) is the set-based, high-level computer language with which all programs and users access data in Oracle Database Express Edition.

SQL is a declarative, or nonprocedural, language; that is, it describes what to do, but not how. You specify the desired result set (for example, the names of current employees), but not how to get it.

See Also:

- Oracle Database Concepts for a complete overview of SQL

- Oracle Database SQL Language Reference for complete information about SQL

About Procedural Language/SQL (PL/SQL)

Procedural Language/SQL (PL/SQL) (pronounced P L sequel) is a native Oracle Database Express Edition extension to SQL. It bridges the gap between declarative and imperative program control by adding procedural elements, such as conditional control and loops.

In PL/SQL, you can declare constants and variables, procedures and functions, types and variables of those types, and triggers. You can handle exceptions (runtime errors). You can create PL/SQL units—procedures, functions, packages, types, and triggers—that are stored in the database for reuse by applications that use any of the Oracle Database Express Edition programmatic interfaces.

The basic unit of a PL/SQL source program is the block, which groups related declarations and statements. A block has an optional declarative part, a required executable part, and an optional exception-handling part.

See Also:

- Oracle Database Concepts for a complete overview of PL/SQL

- Oracle Database PL/SQL Language Reference for complete information about PL/SQL

About Other Client Programs, Languages, and Development Tools

Some other database access clients, languages, and tools that you can use to develop applications are:

- Oracle Application Express

- Oracle Java Database Connectivity (JDBC)

- Hypertext Preprocessor (PHP)

- Oracle Call Interface (OCI)

- Oracle C++ Call Interface (OCCI)

- Open Database Connectivity (ODBC)

- Pro*C/C++ Precompiler

- Pro*COBOL Precompiler

- Microsoft .NET Framework

- Oracle Provider for OLE DB (OraOLEDB)

Note:
Some of the products on the preceding list do not ship with Oracle Database Express Edition and must be downloaded separately.

See Also:

- Oracle Database Concepts for more information about tools for Oracle Database Express Edition developers

- Oracle Database Advanced Application Developer's Guide for information about choosing a programming environment

Oracle Application Express

Oracle Application Express is an application development and deployment tool that enables you to quickly create secure and scalable web applications even if you have limited previous programming experience. The embedded Application Builder tool assembles an HTML interface or a complete application that uses schema objects, such as tables or stored procedures, into a collection of pages that are linked through tabs, buttons, or hypertext links.

See Also:
Oracle Database Express Edition 2 Day + Application Express Developer's Guide for more information about Oracle Application Express

Oracle Java Database Connectivity (JDBC)

Oracle Java Database Connectivity (JDBC) is an API that enables Java to send SQL statements to an object-relational database, such as Oracle Database Express Edition. Oracle Database Express Edition JDBC provides complete support for the JDBC 3.0 and JDBC RowSet (JSR-114) standards, advanced connection caching for both XA and non-XA connections, exposure of SQL and PL/SQL data types to Java, and fast SQL data access.

See Also:
For more information about JDBC:

- Oracle Database Concepts

- Oracle Database Advanced Application Developer's Guide

- Oracle Database Express Edition 2 Day + Java Developer's Guide

Hypertext Preprocessor (PHP)

The Hypertext Preprocessor (PHP) is a powerful interpreted server-side scripting language for quick web application development. PHP is an open source language that is distributed under a BSD-style license. PHP is designed for embedding database access requests directly into HTML pages.

See Also:
Oracle Database Express Edition 2 Day + PHP Developer's Guide for more information about PHP

Oracle Call Interface (OCI)

Oracle Call Interface (OCI) is the native C language API for accessing Oracle Database Express Edition directly from C applications.

The OCI Software Development Kit is also installed as part of the Oracle Instant Client, which enables you to run applications without installing the standard Oracle client or having an ORACLE_HOME. Your applications work without change, using significantly less disk space.

See Also:

- Oracle Database Advanced Application Developer's Guide for more information about OCI

- Oracle Call Interface Programmer's Guide for complete information about OCI

Oracle C++ Call Interface (OCCI)

Oracle C++ Call Interface (OCCI) is the native C++ language API for accessing Oracle Database Express Edition directly from C++ applications. Very similar to the OCI, OCCI supports both relational and object-oriented programming paradigms.

The OCCI Software Development Kit is also installed as part of the Oracle Instant Client, which enables you to run applications without installing the standard Oracle client or having an ORACLE_HOME. Your applications work without change, using significantly less disk space.

See Also:

- Oracle Database Advanced Application Developer's Guide for more information about OCCI

- Oracle C++ Call Interface Programmer's Guide for complete information about OCCI

Open Database Connectivity (ODBC)

Open Database Connectivity (ODBC) is a set of database access APIs that connect to the database, prepare, and then run SQL statements on the database. An application that uses an ODBC driver can access non-uniform data sources, such as spreadsheets and comma-delimited files.

The Oracle ODBC driver conforms to ODBC 3.51 specifications. It supports all core APIs and a subset of Level 1 and Level 2 functions. Microsoft supplies the Driver manager component for the Windows platform.

Like OCI, OCCI, and JDBC, ODBC is part of the Oracle Instant Client installation.

See Also:

- Oracle Database Concepts

- Oracle Services for Microsoft Transaction Server Developer's Guide for Microsoft Windows for information about using the Oracle ODBC driver with Windows

- Oracle Database Administrator's Reference for Linux and UNIX-Based Operating Systems for information about using Oracle ODBC driver on Linux

Pro*C/C++ Precompiler

The Pro*C/C++ precompiler enables you to embed SQL statements in a C or C++ source file. The precompiler accepts the source program as input, translates the embedded SQL statements into standard Oracle runtime library calls, and generates a modified source program that you can compile, link, and run.

See Also:

- Oracle Database Concepts for more information about Oracle precompilers

- Oracle Database Advanced Application Developer's Guide for more information about the Pro*C/C++ precompiler

- Pro*C/C++ Programmer's Guide for complete information about the Pro*C/C++ precompiler

Pro*COBOL Precompiler

The Pro*COBOL precompiler enables you to embed SQL statements in a COBOL source file. The precompiler accepts the source program as input, translates the embedded SQL statements into standard Oracle runtime library calls, and generates a modified source program that you can compile, link, and run.

See Also:

- Oracle Database Concepts for more information about Oracle precompilers

- Oracle Database Advanced Application Developer's Guide for more information about the Pro*COBOL precompiler

- Pro*COBOL Programmer's Guide for complete information about the Pro*COBOL precompiler

Microsoft .NET Framework

The Microsoft .NET Framework is a multilanguage environment for building, deploying, and running applications and XML web services. Its main components are:

- Common Language Runtime (CLR)
The Common Language Runtime (CLR) is a language-neutral development and runtime environment that provides services that help manage running applications.

- Framework Class Libraries (FCL)
The Framework Class Libraries (FCL) provide a consistent, object-oriented library of prepackaged functionality.

Oracle Data Provider for .NET (ODP.NET)

Oracle Data Provider for .NET (ODP.NET) provides fast and efficient ADO.NET data access from .NET applications to Oracle Database Express Edition. ODP.NET allows developers to take advantage of advanced Oracle Database functionality that exists in Oracle Database Express Edition, including SecureFiles, XML DB, and Advanced Queuing.

Oracle Developer Tools for Visual Studio (ODT)

Oracle Developer Tools for Visual Studio (ODT) is a set of application tools that integrate with the Visual Studio environment. These tools provide graphic user interface access to Oracle functionality, enable the user to perform a wide range of application development tasks, and improve development productivity and ease of use. Oracle Developer Tools supports the programming and implementation of .NET stored procedures using Visual Basic, C#, and other .NET languages.

.NET Stored Procedures

Oracle Database Extensions for .NET is a database option for Oracle Database Express Edition on Windows. It makes it possible to build and run .NET stored procedures or functions with Oracle Database for Microsoft Windows using Visual Basic .NET or Visual C#.

After building .NET procedures and functions into a .NET assembly, you can deploy them in Oracle Database using the Oracle Deployment Wizard for .NET, a component of the Oracle Developer Tools for Visual Studio.

Oracle Providers for ASP.NET

Oracle Providers for ASP.NET offer ASP.NET developers an easy way to store state common to web applications within Oracle Database Express Edition. These providers are modeled on existing Microsoft ASP.NET providers, sharing similar schema and programming interfaces to provide .NET developers a familiar interface. Oracle supports the Membership, Profile, Role, and other providers.

See Also:

- Oracle Database Express Edition 2 Day + .NET Developer's Guide for Microsoft Windows

- Oracle Data Provider for .NET Developer's Guide for Microsoft Windows

- Oracle Database Extensions for .NET Developer's Guide for Microsoft Windows

- Oracle Database Advanced Application Developer's Guide

Oracle Provider for OLE DB (OraOLEDB)

Oracle Provider for OLE DB (OraOLEDB) is an open standard data access methodology that uses a set of Component Object Model (COM) interfaces for accessing and manipulating different types of data. These interfaces are available from various database providers.

See Also:
Oracle Provider for OLE DB Developer's Guide for Microsoft Windows for more information about OraOLEDB

About Sample Schema HR

The HR schema is a sample schema that can be installed as part of Oracle Database Express Edition. This schema contains information about employees—their departments, locations, work histories, and related information. Like all schemas, the HR schema has tables, views, indexes, procedures, functions, and other attributes of a database schema.

The examples and tutorials in this document use the HR schema.

See Also:

- Oracle Database Sample Schemas for a complete description of the HR schema

- "Connecting to Oracle Database Express Edition as User HR" for instructions for connecting to Oracle Database Express Edition as the user HR

2 Connecting to Oracle Database Express Edition and Exploring It

You can connect to Oracle Database Express Edition only through a client program, such as SQL*Plus or SQL Developer.

Note:
After connecting to Oracle Database Express Edition through a client program, you enter and run commands in that client program. For details, see the documentation for your client program.

This chapter contains:

- Connecting to Oracle Database Express Edition from SQL*Plus

- Connecting to Oracle Database Express Edition from SQL Developer

- Connecting to Oracle Database Express Edition as User HR

- Exploring Oracle Database Express Edition with SQL*Plus

- Exploring Oracle Database Express Edition with SQL Developer

- Selecting Table Data

Connecting to Oracle Database Express Edition from SQL*Plus

SQL*Plus is a client program with which you can access Oracle Database Express Edition. This section shows how to start SQL*Plus and connect to Oracle Database Express Edition.

Note:
For steps 3 and 4 of the following procedure, you need a user name and password.

To connect to Oracle Database Express Edition from SQL*Plus:

1. If you are on a Windows system, display a Windows command prompt.

2. At the command prompt, type sqlplus and then press the key Enter.

3. At the user name prompt, type your user name and then press the key Enter.

4. At the password prompt, type your password and then press the key Enter.

Note:
For security, your password is not visible on your screen.

The system connects you to an Oracle Database Express Edition instance.

You are in the SQL*Plus environment. At the SQL> prompt, you can enter and run SQL*Plus commands, SQL statements, PL/SQL statements, and operating system commands.

To exit SQL*Plus, type exit and press the key Enter.

Note:
Exiting SQL*Plus ends the SQL*Plus session, but does not shut down the Oracle Database Express Edition instance.

Example 2-1 starts SQL*Plus, connects to Oracle Database Express Edition, runs a SQL SELECT statement, and exits SQL*Plus. User input is bold.

Example 2-1 Connecting to Oracle Database from SQL*Plus

> sqlplus
SQL*Plus: Release 12.1.0.1.0 Production on Thu Dec 27 07:43:41 2012

Copyright (c) 1982, 2012, Oracle.  All rights reserved.

Enter user-name: your_user_name
Enter password: your_password

Connected to:
Oracle Database 12c Enterprise Edition Release - 12.1.0.1.0 64bit Production

SQL> select count(*) from employees;

COUNT(*)
----------
107

SQL> exit

Disconnected from Oracle Database 12c Enterprise Edition Release - 12.1.0.1.0 64bit Production
>

See Also:

- "Connecting to Oracle Database Express Edition as User HR from SQL*Plus"

- "About SQL*Plus" for a brief description of SQL*Plus

- SQL*Plus User's Guide and Reference for more information about starting SQL*Plus and connecting to Oracle Database Express Edition

Connecting to Oracle Database Express Edition from SQL Developer

SQL Developer is a client program with which you can access Oracle Database Express Edition. With Oracle Database Express Edition 11g Release 2 (11.2), Oracle recommends using SQL Developer version 4.0 or later, which you can download from:

http://www.oracle.com/technetwork/developer-tools/sql-developer/downloads/

This section assumes that SQL Developer is installed on your system, and shows how to start it and connect to Oracle Database Express Edition. If SQL Developer is not installed on your system, then see Oracle SQL Developer User's Guide for installation instructions.

Note:
For the following procedure:

- If you're using a SQL Developer kit that does not include the JDK, then the first time you start SQL Developer on your system, you must provide the full path to java.exe in step 1.

- For step 3, you need a user name and password.

To connect to Oracle Database Express Edition from SQL Developer:

1. Start SQL Developer.

For instructions, see Oracle SQL Developer User's Guide.

If this is the first time you have started SQL Developer on your system, you are prompted to enter the full path to java.exe (for example, C:\Program Files\Java\jdk1.6.0_021\bin\java.exe). Either type the full path after the prompt or browse to it, and then press the key Enter.

2. In the Connections frame, click the icon New Connection.

3. In the New/Select Database Connection window:

1. Type the appropriate values in the fields Connection Name, Username, and Password.
For security, the password characters that you type appear as asterisks.

Near the Password field is the check box Save Password. By default, it is deselected. Oracle recommends accepting the default.

2. If the Oracle pane is not showing, click the tab Oracle.

3. In the Oracle pane, accept the default values.
(The default values are: Connection Type, Basic; Role, default, Hostname, localhost; Port, 1521; SID option, selected; SID field, xe.)

4. Click the button Test.
The connection is tested. If the connection succeeds, the Status indicator changes from blank to Success.

5. If the test succeeded, click the button Connect.
The New/Select Database Connection window closes. The Connections frame shows the connection whose name you entered in the Connection Name field in step 3.

You are in the SQL Developer environment.

To exit SQL Developer, select Exit from the File menu.

Note:
Exiting SQL Developer ends the SQL Developer session, but does not shut down the Oracle Database Express Edition instance. The next time you start SQL Developer, the connection you created using the preceding procedure still exists. SQL Developer prompts you for the password that you supplied in step 3 (unless you selected the check box Save Password).

See Also:

- "Connecting to Oracle Database Express Edition as User HR from SQL Developer"

- "About SQL Developer" for a brief description of SQL Developer

- Oracle SQL Developer User's Guide for more information about using SQL Developer to create connections to Oracle Database Express Edition

Connecting to Oracle Database Express Edition as User HR

This section shows how to unlock the HR account and connect to Oracle Database Express Edition as the user HR, who owns the HR sample schema that the examples and tutorials in this document use.

To do the tutorials and examples in this document, you must connect to Oracle Database Express Edition as the user HR.

This section contains:

- Unlocking the HR Account

- Connecting to Oracle Database Express Edition as User HR from SQL*Plus

- Connecting to Oracle Database Express Edition as User HR from SQL Developer

Unlocking the HR Account

This section shows how to unlock the HR account and reset its password.

By default, when the HR schema is installed, the HR account is locked and its password is expired. You can connect to Oracle Database as the user HR only if the HR account is unlocked.

Note:
For the following procedure, you need the name and password of a user who has the ALTER USER system privilege.

To unlock the HR account and reset its password:

1. Using SQL*Plus, connect to Oracle Database Express Edition as a user with the ALTER USER system privilege.

2. At the SQL> prompt, unlock the HR account and reset its password:

Caution:
Choose a secure password. For guidelines for secure passwords, see Oracle Database Security Guide.

ALTER USER HR ACCOUNT UNLOCK IDENTIFIED BY password;

The system responds:

User altered.

The HR account is unlocked and its password is password.

Now you can connect to Oracle Database Express Edition as user HR with the password password.

See Also:

- Oracle Database 2 Day + Security Guide for information about predefined user accounts provided by Oracle Database Express Edition, including HR

- Oracle SQL Developer User's Guide for information about accessing SQL*Plus within SQL Developer

Connecting to Oracle Database Express Edition as User HR from SQL*Plus

This section shows how to connect to Oracle Database Express Edition as the user HR from SQL*Plus.

Note:
If the HR account is locked, see "Unlocking the HR Account" and then return to this section.

To connect to Oracle Database Express Edition as user HR from SQL*Plus:

Note:
For this task, you need the password for the HR account.

1. If you are connected to Oracle Database Express Edition, close your current connection.

2. Follow the directions in "Connecting to Oracle Database Express Edition from SQL*Plus", entering the user name HR at step 3 and the password for the HR account at step 4.
You are now connected to Oracle Database Express Edition as the user HR.

See Also:
SQL*Plus User's Guide and Reference for an example of using SQL*Plus to create an HR connection

Connecting to Oracle Database Express Edition as User HR from SQL Developer

This section shows how to connect to Oracle Database Express Edition as the user HR from SQL Developer.

Note:
If the HR account is locked, see "Unlocking the HR Account" and then return to this section.

To connect to Oracle Database Express Edition as user HR from SQL Developer:

Note:
For this task, you need the password for the HR account.

Follow the directions in "Connecting to Oracle Database Express Edition from SQL Developer", entering the following values at steps 3:

- For Connection Name, enter hr_conn.
(You can enter a different name, but the tutorials in this document assume that you named the connection hr_conn.)

- For Username, enter HR.

- For Password, enter the password for the HR account.

You are now connected to Oracle Database Express Edition as the user HR.

Exploring Oracle Database Express Edition with SQL*Plus

This section contains:

- Viewing HR Schema Objects with SQL*Plus

- Viewing EMPLOYEES Table Properties and Data with SQL*Plus

Note:
If you are not connected to Oracle Database Express Edition as user HR from SQL*Plus, see "Connecting to Oracle Database Express Edition as User HR from SQL*Plus" and then return to this section.

Viewing HR Schema Objects with SQL*Plus

With SQL*Plus, you can view the objects that belong to the HR schema by querying the static data dictionary view USER_OBJECTS.

Example 2-2 shows how to view the names and data types of the objects that belong to the HR schema.

Example 2-2 Viewing HR Schema Objects with SQL*Plus

COLUMN OBJECT_NAME FORMAT A25
COLUMN OBJECT_TYPE FORMAT A25

SELECT OBJECT_NAME, OBJECT_TYPE FROM USER_OBJECTS
ORDER BY OBJECT_TYPE, OBJECT_NAME;

Result is similar to:

OBJECT_NAME               OBJECT_TYPE
------------------------- -------------------------
COUNTRY_C_ID_PK           INDEX
DEPT_ID_PK                INDEX
DEPT_LOCATION_IX          INDEX
EMP_DEPARTMENT_IX         INDEX
EMP_EMAIL_UK              INDEX
EMP_EMP_ID_PK             INDEX
EMP_JOB_IX                INDEX
EMP_MANAGER_IX            INDEX
EMP_NAME_IX               INDEX
JHIST_DEPARTMENT_IX       INDEX
JHIST_EMPLOYEE_IX         INDEX
JHIST_EMP_ID_ST_DATE_PK   INDEX
JHIST_JOB_IX              INDEX
JOB_ID_PK                 INDEX
LOC_CITY_IX               INDEX
LOC_COUNTRY_IX            INDEX
LOC_ID_PK                 INDEX
LOC_STATE_PROVINCE_IX     INDEX
REG_ID_PK                 INDEX
ADD_JOB_HISTORY           PROCEDURE
SECURE_DML                PROCEDURE
DEPARTMENTS_SEQ           SEQUENCE
EMPLOYEES_SEQ             SEQUENCE
LOCATIONS_SEQ             SEQUENCE
COUNTRIES                 TABLE
DEPARTMENTS               TABLE
EMPLOYEES                 TABLE
JOBS                      TABLE
JOB_HISTORY               TABLE
LOCATIONS                 TABLE
REGIONS                   TABLE
SECURE_EMPLOYEES          TRIGGER
UPDATE_JOB_HISTORY        TRIGGER
EMP_DETAILS_VIEW          VIEW

34 rows selected.

See Also:

- Oracle Database Reference for information about USER_OBJECTS

- "Selecting Table Data" for information about using queries to view table data

- "About Sample Schema HR" for general information about the schema HR

Viewing EMPLOYEES Table Properties and Data with SQL*Plus

With SQL*Plus, you can use the SQL*Plus command DESCRIBE to view the properties of the columns of the EMPLOYEES table in the HR schema and the SQL statement SELECT to view the data. To view other properties of the table, use static data dictionary views (for example, USER_CONSTRAINTS, USER_INDEXES, and USER_TRIGGERS).

Example 2-3 shows how to view the properties of the EMPLOYEES table in the HR schema.

Example 2-3 Viewing EMPLOYEES Table Properties with SQL*Plus

DESCRIBE EMPLOYEES

Result:

Name                                      Null?    Type
----------------------------------------- -------- -------------

EMPLOYEE_ID                               NOT NULL NUMBER(6)
FIRST_NAME                                         VARCHAR2(20)
LAST_NAME                                 NOT NULL VARCHAR2(25)
EMAIL                                     NOT NULL VARCHAR2(25)
PHONE_NUMBER                                       VARCHAR2(20)
HIRE_DATE                                 NOT NULL DATE
JOB_ID                                    NOT NULL VARCHAR2(10)
SALARY                                             NUMBER(8,2)
COMMISSION_PCT                                     NUMBER(2,2)
MANAGER_ID                                         NUMBER(6)
DEPARTMENT_ID                                      NUMBER(4)

Example 2-4 shows how to view some data in the EMPLOYEES table in the HR schema.

Example 2-4 Viewing EMPLOYEES Table Data with SQL*Plus

COLUMN FIRST_NAME FORMAT A20
COLUMN LAST_NAME FORMAT A25
COLUMN PHONE_NUMBER FORMAT A20

SELECT LAST_NAME, FIRST_NAME, PHONE_NUMBER FROM EMPLOYEES
ORDER BY LAST_NAME;

Result is similar to:

LAST_NAME                 FIRST_NAME           PHONE_NUMBER
------------------------- -------------------- --------------------
Abel                      Ellen                011.44.1644.429267
Ande                      Sundar               011.44.1346.629268
Atkinson                  Mozhe                650.124.6234
Austin                    David                590.423.4569
Baer                      Hermann              515.123.8888
Baida                     Shelli               515.127.4563
Banda                     Amit                 011.44.1346.729268
Bates                     Elizabeth            011.44.1343.529268
...
Urman                     Jose Manuel          515.124.4469
Vargas                    Peter                650.121.2004
Vishney                   Clara                011.44.1346.129268
Vollman                   Shanta               650.123.4234
Walsh                     Alana                650.507.9811
Weiss                     Matthew              650.123.1234
Whalen                    Jennifer             515.123.4444
Zlotkey                   Eleni                011.44.1344.429018

107 rows selected.

See Also:

- SQL*Plus User's Guide and Reference for information about DESCRIBE

- "Selecting Table Data" for information about using queries to view table data

- Oracle Database Reference for information about static data dictionary views

Exploring Oracle Database Express Edition with SQL Developer

This section contains:

- Tutorial: Viewing HR Schema Objects with SQL Developer

- Tutorial: Viewing EMPLOYEES Table Properties and Data with SQL Developer

Tutorial: Viewing HR Schema Objects with SQL Developer

This tutorial shows how to use SQL Developer to view the objects that belong to the HR schema—that is, how to browse the HR schema.

Note:
If you are not connected to Oracle Database Express Edition as user HR from SQL Developer, see "Connecting to Oracle Database Express Edition as User HR from SQL Developer" and then return to this tutorial.

To browse the HR schema:

1. In the Connections frame, to the left of the hr_conn icon, click the plus sign (+).
If you are not connected to the database, the Connection Information window opens. If you are connected to the database, the hr_conn information expands (see the information that follows "Click OK" in step 2).

2. If the Connection Information window opens:

1. In the User Name field, enter hr.

2. In the Password field, enter the password for the user hr.

3. Click OK.

The hr_conn information expands: The plus sign becomes a minus sign (-), and under the hr_conn icon, a list of schema object types appears—Tables, Views, Indexes, and so on. (If you click the minus sign, the hr_conn information collapses: The minus sign becomes a plus sign, and the list disappears.)

See Also:

- Oracle SQL Developer User's Guide for more information about the SQL Developer user interface

- "About Sample Schema HR" for general information about schema HR

Tutorial: Viewing EMPLOYEES Table Properties and Data with SQL Developer

This tutorial shows how to use SQL Developer to view the properties and data of the EMPLOYEES table in the HR schema.

Note:
If you are not browsing the HR schema, see "Tutorial: Viewing HR Schema Objects with SQL Developer" and then return to this tutorial.

To view the properties and data of the EMPLOYEES table:

1. In the Connections frame, expand Tables.
Under Tables, a list of the tables in the HR schema appears.

2. Select the table EMPLOYEES.
In the right frame of the Oracle SQL Developer window, in the Columns pane, a list of all columns of this table appears. To the right of each column are its properties—name, data type, and so on. (To see all column properties, move the horizontal scroll bar to the right.)

3. In the right frame, click the tab Data.
The Data pane appears, showing a numbered list of all records in this table. (To see more records, move the vertical scroll bar down. To see more columns of the records, move the horizontal scroll bar to the right.)

4. In the right frame, click the tab Constraints.
The Constraints pane appears, showing a list of all constraints on this table. To the right of each constraint are its properties—name, type, search condition, and so on. (To see all constraint properties, move the horizontal scroll bar to the right.)

5. Explore the other properties by clicking on the appropriate tabs.
To see the SQL statement for creating the EMPLOYEES table, click the SQL tab. The SQL statement appears in a pane named EMPLOYEES. To close this pane, click the x to the right of the name EMPLOYEES.

See Also:
Oracle SQL Developer User's Guide for more information about the SQL Developer user interface

Selecting Table Data

This section contains:

- About Queries

- Running Queries in SQL Developer

- Tutorial: Selecting Specific Columns of a Table

- Tutorial: Selecting Specific Columns of a Table

- Displaying Selected Columns Under New Headings

- Selecting Data that Satisfies Specified Conditions

- Sorting Selected Data

- Selecting Data from Multiple Tables

- Using Operators and Functions in Queries

Note:
To do the tutorials and examples in this section, you must be connected to Oracle Database Express Edition as the user HR from SQL Developer. For instructions, see "Connecting to Oracle Database Express Edition as User HR from SQL Developer".

About Queries

A query, or SQL SELECT statement, selects data from one or more tables or views.

The simplest form of query has this syntax:

SELECT select_list FROM source_list

The select_list specifies the columns from which the data is to be selected, and the source_list specifies the tables or views that have these columns.

A query nested within another SQL statement is called a subquery.

In the SQL*Plus environment, you can enter a query (or any other SQL statement) after the SQL> prompt.

In the SQL Developer environment, you can enter a query (or any other SQL statement) in the Worksheet.

Note:
When the result of a query is displayed, records can be in any order, unless you specify their order with the ORDER BY clause. For more information, see "Sorting Selected Data".

See Also:

- Oracle Database SQL Language Reference for more information about queries and subqueries

- Oracle Database SQL Language Reference for more information about the SELECT statement

- SQL*Plus User's Guide and Reference for more information about the SQL*Plus command line interface

- Oracle SQL Developer User's Guide for information about using the Worksheet in SQL Developer

Running Queries in SQL Developer

This section explains how to run queries in SQL Developer, by using the Worksheet.

Note:
The Worksheet is not limited to queries; you can use it to run any SQL statement.

To run queries in SQL Developer:

1. If the right frame of SQL Developer shows the hr_conn pane:

1. If the Worksheet subpane does not show, click the tab Worksheet.

2. Go to step 3.

2. Click the icon SQL Worksheet.

3. If the Select Connection window opens:

1. If the Connection field does not have the value hr_conn, select that value from the menu.

2. Click OK.

A pane appears with a tab labeled hr_conn and two subpanes, Worksheet and Query Builder. In the Worksheet, you can enter a SQL statement.

4. In the Worksheet, type a query (a SELECT statement).

5. Click the icon Run Statement.
The query runs. Under the Worksheet, the Query Result pane appears, showing the query result.

6. Under the hr_conn tab, click the icon Clear.
The query disappears, and you can enter another SQL statement in the Worksheet. When you run another SQL statement, its result appears in the Query Result pane, replacing the result of the previously run SQL statement.

See Also:
Oracle SQL Developer User's Guide for information about using the Worksheet in SQL Developer

Tutorial: Selecting All Columns of a Table

This tutorial shows how to select all columns of the EMPLOYEES table.

To select all columns of the EMPLOYEES Table:

1. If a pane with the tab hr_conn is there, select it. Otherwise, click the icon SQL Worksheet, as in "Running Queries in SQL Developer".

2. In the Worksheet, enter this query:

SELECT * FROM EMPLOYEES;

3. Click the icon Run Statement.
The query runs. Under the Worksheet, the Query Result pane appears, showing all columns of the EMPLOYEES table.

Caution:
Be very careful about using SELECT * on tables with columns that store sensitive data, such as passwords or credit card information.

See Also:
"Tutorial: Viewing EMPLOYEES Table Properties and Data with SQL Developer" for information about another way to view table data with SQL Developer

Tutorial: Selecting Specific Columns of a Table

This tutorial shows how to select only the columns FIRST_NAME, LAST_NAME, and DEPARTMENT_ID of the EMPLOYEES table.

To select only FIRST_NAME, LAST_NAME, and DEPARTMENT_ID:

1. If a pane with the tab hr_conn is there, select it. Otherwise, click the icon SQL Worksheet, as in "Running Queries in SQL Developer".

2. If the Worksheet pane contains a query, clear the query by clicking the icon Clear.

3. In the Worksheet, enter this query:

SELECT FIRST_NAME, LAST_NAME, DEPARTMENT_ID
FROM EMPLOYEES;

4. Click the icon Run Statement.
The query runs. Under the Worksheet, the Query Result pane appears, showing the results of the query, which are similar to:

FIRST_NAME           LAST_NAME                 DEPARTMENT_ID
-------------------- ------------------------- -------------
Donald               OConnell                             50
Douglas              Grant                                50
Jennifer             Whalen                               10
Michael              Hartstein                            20
Pat                  Fay                                  20
Susan                Mavris                               40
Hermann              Baer                                 70
Shelley              Higgins                             110
William              Gietz                               110
Steven               King                                 90
Neena                Kochhar                              90

FIRST_NAME           LAST_NAME                 DEPARTMENT_ID
-------------------- ------------------------- -------------
Lex                  De Haan                              90
...
Kevin                Feeney                               50

107 rows selected.

Displaying Selected Columns Under New Headings

When query results are displayed, the default column heading is the column name. To display a column under a new heading, specify the new heading (alias) immediately after the name of the column. The alias renames the column for the duration of the query, but does not change its name in the database.

The query in Example 2-5 selects the same columns as the query in "Tutorial: Selecting Specific Columns of a Table", but it also specifies aliases for them. Because the aliases are not enclosed in double quotation marks, they are displayed in uppercase letters.

Example 2-5 Displaying Selected Columns Under New Headings

SELECT FIRST_NAME First, LAST_NAME last, DEPARTMENT_ID DepT
FROM EMPLOYEES;

Result is similar to:

FIRST                LAST                            DEPT
-------------------- ------------------------- ----------
Donald               OConnell                          50
Douglas              Grant                             50
Jennifer             Whalen                            10
Michael              Hartstein                         20
Pat                  Fay                               20
Susan                Mavris                            40
Hermann              Baer                              70
Shelley              Higgins                          110
William              Gietz                            110
Steven               King                              90
Neena                Kochhar                           90

FIRST                LAST                            DEPT
-------------------- ------------------------- ----------
Lex                  De Haan                           90
...
Kevin                Feeney                            50

107 rows selected.

If you enclose column aliases in double quotation marks, case is preserved, and the aliases can include spaces, as in Example 2-6.

Example 2-6 Preserving Case and Including Spaces in Column Aliases

SELECT FIRST_NAME "Given Name", LAST_NAME "Family Name"
FROM EMPLOYEES;

Result is similar to:

Given Name           Family Name
-------------------- -------------------------
Donald               OConnell
Douglas              Grant
Jennifer             Whalen
Michael              Hartstein
Pat                  Fay
Susan                Mavris
Hermann              Baer
Shelley              Higgins
William              Gietz
Steven               King
Neena                Kochhar

Given Name           Family Name
-------------------- -------------------------
Lex                  De Haan
...
Kevin                Feeney

107 rows selected.

See Also:
Oracle Database SQL Language Reference for more information about the SELECT statement, including the column alias (c_alias)

Selecting Data that Satisfies Specified Conditions

To select only data that matches a specified condition, include the WHERE clause in the SELECT statement. The condition in the WHERE clause can be any SQL condition (for information about SQL conditions, see Oracle Database SQL Language Reference).

The query in Example 2-7 selects data only for employees in department 90.

Example 2-7 Selecting Data from One Department

SELECT FIRST_NAME, LAST_NAME, DEPARTMENT_ID
FROM EMPLOYEES
WHERE DEPARTMENT_ID = 90;

Result is similar to:

FIRST_NAME           LAST_NAME                 DEPARTMENT_ID
-------------------- ------------------------- -------------
Steven               King                                 90
Neena                Kochhar                              90
Lex                  De Haan                              90

3 rows selected.

To select data only for employees in departments 100, 110, and 120, use this WHERE clause:

WHERE DEPARTMENT_ID IN (100, 110, 120);

The query in Example 2-8 selects data only for employees whose last names start with "Ma".

Example 2-8 Selecting Data for Last Names that Start with the Same Substring

SELECT FIRST_NAME, LAST_NAME
FROM EMPLOYEES
WHERE LAST_NAME LIKE 'Ma%';

Result is similar to:

FIRST_NAME           LAST_NAME
-------------------- -------------------------
Jason                Mallin
Steven               Markle
James                Marlow
Mattea               Marvins
Randall              Matos
Susan                Mavris

6 rows selected.

To select data only for employees whose last names include "ma", use this WHERE clause:

WHERE LAST_NAME LIKE '%ma%';

The query in Example 2-9 tests for two conditions—whether the salary is at least 11000, and whether the commission percentage is not null.

Example 2-9 Selecting Data that Satisfies Two Conditions

SELECT FIRST_NAME, LAST_NAME, SALARY, COMMISSION_PCT "%"
FROM EMPLOYEES
WHERE (SALARY >= 11000) AND (COMMISSION_PCT IS NOT NULL);

Result is similar to:

FIRST_NAME           LAST_NAME                     SALARY          %
-------------------- ------------------------- ---------- ----------
John                 Russell                        14000         .4
Karen                Partners                       13500         .3
Alberto              Errazuriz                      12000         .3
Gerald               Cambrault                      11000         .3
Lisa                 Ozer                           11500        .25
Ellen                Abel                           11000         .3

6 rows selected.

See Also:

- Oracle Database SQL Language Reference for more information about the SELECT statement, including the WHERE clause

- Oracle Database SQL Language Reference for more information about SQL conditions

Sorting Selected Data

When query results are displayed, records can be in any order, unless you specify their order with the ORDER BY clause.

The query results in Example 2-10 are sorted by LAST_NAME, in ascending order (the default).

Alternatively, in SQL Developer, you can omit the ORDER BY clause and double-click the name of the column to sort.

Example 2-10 Sorting Selected Data by LAST_NAME

SELECT FIRST_NAME, LAST_NAME, HIRE_DATE
FROM EMPLOYEES
ORDER BY LAST_NAME;

Result:

FIRST_NAME           LAST_NAME                 HIRE_DATE
-------------------- ------------------------- ---------
Ellen                Abel                      11-MAY-04
Sundar               Ande                      24-MAR-08
Mozhe                Atkinson                  30-OCT-05
David                Austin                    25-JUN-05
Hermann              Baer                      07-JUN-02
Shelli               Baida                     24-DEC-05
Amit                 Banda                     21-APR-08
Elizabeth            Bates                     24-MAR-07
...
FIRST_NAME           LAST_NAME                 HIRE_DATE
-------------------- ------------------------- ---------
Jose Manuel          Urman                     07-MAR-06
Peter                Vargas                    09-JUL-06
Clara                Vishney                   11-NOV-05
Shanta               Vollman                   10-OCT-05
Alana                Walsh                     24-APR-06
Matthew              Weiss                     18-JUL-04
Jennifer             Whalen                    17-SEP-03
Eleni                Zlotkey                   29-JAN-08

107 rows selected

The sort criterion need not be included in the select list, as Example 2-11 shows.

Example 2-11 Sorting Selected Data by an Unselected Column

SELECT FIRST_NAME, HIRE_DATE
FROM EMPLOYEES
ORDER BY LAST_NAME;

Result:

FIRST_NAME           HIRE_DATE
-------------------- ---------
Ellen                11-MAY-04
Sundar               24-MAR-08
Mozhe                30-OCT-05
David                25-JUN-05
Hermann              07-JUN-02
Shelli               24-DEC-05
Amit                 21-APR-08
Elizabeth            24-MAR-07
...
FIRST_NAME           HIRE_DATE
-------------------- ---------
Jose Manuel          07-MAR-06
Peter                09-JUL-06
Clara                11-NOV-05
Shanta               10-OCT-05
Alana                24-APR-06
Matthew              18-JUL-04
Jennifer             17-SEP-03
Eleni                29-JAN-08

107 rows selected.

See Also:
Oracle Database SQL Language Reference for more information about the SELECT statement, including the ORDER BY clause

Selecting Data from Multiple Tables

Suppose that you want to select the FIRST_NAME, LAST_NAME, and DEPARTMENT_NAME of every employee. FIRST_NAME and LAST_NAME are in the EMPLOYEES table, and DEPARTMENT_NAME is in the DEPARTMENTS table. Both tables have DEPARTMENT_ID. You can use the query in Example 2-12. Such a query is called a join.

Example 2-12 Selecting Data from Two Tables (Joining Two Tables)

SELECT EMPLOYEES.FIRST_NAME "First",
EMPLOYEES.LAST_NAME "Last",
DEPARTMENTS.DEPARTMENT_NAME "Dept. Name"
FROM EMPLOYEES, DEPARTMENTS
WHERE EMPLOYEES.DEPARTMENT_ID = DEPARTMENTS.DEPARTMENT_ID
ORDER BY DEPARTMENTS.DEPARTMENT_NAME, EMPLOYEES.LAST_NAME;

Result:

First                Last                      Dept. Name
-------------------- ------------------------- ------------------------------
William              Gietz                     Accounting
Shelley              Higgins                   Accounting
Jennifer             Whalen                    Administration
Lex                  De Haan                   Executive
Steven               King                      Executive
Neena                Kochhar                   Executive
John                 Chen                      Finance
...
Jose Manuel          Urman                     Finance
Susan                Mavris                    Human Resources
David                Austin                    IT
...
Valli                Pataballa                 IT
Pat                  Fay                       Marketing
Michael              Hartstein                 Marketing
Hermann              Baer                      Public Relations
Shelli               Baida                     Purchasing
...
Sigal                Tobias                    Purchasing
Ellen                Abel                      Sales
...
Eleni                Zlotkey                   Sales
Mozhe                Atkinson                  Shipping
...
Matthew              Weiss                     Shipping

106 rows selected.

Table-name qualifiers are optional for column names that appear in only one table of a join, but are required for column names that appear in both tables. The following query is equivalent to the query in Example 2-12:

SELECT FIRST_NAME "First",
LAST_NAME "Last",
DEPARTMENT_NAME "Dept. Name"
FROM EMPLOYEES, DEPARTMENTS
WHERE EMPLOYEES.DEPARTMENT_ID = DEPARTMENTS.DEPARTMENT_ID
ORDER BY DEPARTMENT_NAME, LAST_NAME;

To make queries that use qualified column names more readable, use table aliases, as in the following example:

SELECT FIRST_NAME "First",
LAST_NAME "Last",
DEPARTMENT_NAME "Dept. Name"
FROM EMPLOYEES e, DEPARTMENTS d
WHERE e.DEPARTMENT_ID = d.DEPARTMENT_ID
ORDER BY d.DEPARTMENT_NAME, e.LAST_NAME;

Although you create the aliases in the FROM clause, you can use them earlier in the query, as in the following example:

SELECT e.FIRST_NAME "First",
e.LAST_NAME "Last",
d.DEPARTMENT_NAME "Dept. Name"
FROM EMPLOYEES e, DEPARTMENTS d
WHERE e.DEPARTMENT_ID = d.DEPARTMENT_ID
ORDER BY d.DEPARTMENT_NAME, e.LAST_NAME;

See Also:
Oracle Database SQL Language Reference for more information about joins

Using Operators and Functions in Queries

The select_list of a query can include SQL expressions, which can include SQL operators and SQL functions. These operators and functions can have table data as operands and arguments. The SQL expressions are evaluated, and their values appear in the results of the query.

This section contains:

- Using Arithmetic Operators in Queries

- Using Numeric Functions in Queries

- Using the Concatenation Operator in Queries

- Using Character Functions in Queries

- Using Datetime Functions in Queries

- Using Conversion Functions in Queries

- Using Aggregate Functions in Queries

- Using NULL-Related Functions in Queries

- Using CASE Expressions in Queries

- Using the DECODE Function in Queries

See Also:

- Oracle Database SQL Language Reference for more information about SQL operators

- Oracle Database SQL Language Reference for more information about SQL functions

Using Arithmetic Operators in Queries

SQL supports the basic arithmetic operators: + (addition), - (subtraction), * (multiplication), and / (division).

The query in Example 2-13 displays LAST_NAME, SALARY (monthly pay), and annual pay for each employee in department 90, in descending order of SALARY.

Example 2-13 Using an Arithmetic Expression in a Query

SELECT LAST_NAME,
SALARY "Monthly Pay",
SALARY * 12 "Annual Pay"
FROM EMPLOYEES
WHERE DEPARTMENT_ID = 90
ORDER BY SALARY DESC;

Result:

LAST_NAME                 Monthly Pay Annual Pay
------------------------- ----------- ----------
King                            24000     288000
De Haan                         17000     204000
Kochhar                         17000     204000

Using Numeric Functions in Queries

Numeric functions accept numeric input and return numeric values. Each numeric function returns a single value for each row that is evaluated. The numeric functions that SQL supports are listed and described in Oracle Database SQL Language Reference.

The query in Example 2-14 uses the numeric function ROUND to display the daily pay of each employee in department 100, rounded to the nearest cent.

Example 2-14 Rounding Numeric Data

SELECT LAST_NAME,
ROUND (((SALARY * 12)/365), 2) "Daily Pay"
FROM EMPLOYEES
WHERE DEPARTMENT_ID = 100
ORDER BY LAST_NAME;

Result:

LAST_NAME                  Daily Pay
------------------------- ----------
Chen                          269.59
Faviet                        295.89
Greenberg                     394.52
Popp                          226.85
Sciarra                       253.15
Urman                         256.44

6 rows selected.

The query in Example 2-15 uses the numeric function TRUNC to display the daily pay of each employee in department 100, truncated to the nearest dollar.

Example 2-15 Truncating Numeric Data

SELECT LAST_NAME,
TRUNC ((SALARY * 12)/365) "Daily Pay"
FROM EMPLOYEES
WHERE DEPARTMENT_ID = 100
ORDER BY LAST_NAME;

Result:

LAST_NAME                  Daily Pay
------------------------- ----------
Chen                             269
Faviet                           295
Greenberg                        394
Popp                             226
Sciarra                          253
Urman                            256

6 rows selected.

See Also:
Oracle Database SQL Language Reference for more information about SQL numeric functions

Using the Concatenation Operator in Queries

The concatenation operator (||) combines two strings into one string, by appending the second string to the first. For example, 'a'||'b'='ab'. You can use this operator to combine information from two columns or expressions in the same column of the report, as in the query in Example 2-16.

Example 2-16 Concatenating Character Data

SELECT FIRST_NAME || ' ' || LAST_NAME "Name"
FROM EMPLOYEES
WHERE DEPARTMENT_ID = 100
ORDER BY LAST_NAME;

Result:

Name
----------------------------------------------
John Chen
Daniel Faviet
Nancy Greenberg
Luis Popp
Ismael Sciarra
Jose Manuel Urman

6 rows selected.

See Also:
Oracle Database SQL Language Reference for more information about the concatenation operator

Using Character Functions in Queries

Character functions accept character input. Most return character values, but some return numeric values. Each character function returns a single value for each row that is evaluated. The character functions that SQL supports are listed and described in Oracle Database SQL Language Reference.

The functions UPPER, INITCAP, and LOWER display their character arguments in uppercase, initial capital, and lowercase, respectively.

The query in Example 2-17 displays LAST_NAME in uppercase, FIRST_NAME with the first character in uppercase and all others in lowercase, and EMAIL in lowercase.

Example 2-17 Changing the Case of Character Data

SELECT UPPER(LAST_NAME) "Last",
INITCAP(FIRST_NAME) "First",
LOWER(EMAIL) "E-Mail"
FROM EMPLOYEES
WHERE DEPARTMENT_ID = 100
ORDER BY EMAIL;

Result:

Last                      First                E-Mail
------------------------- -------------------- -------------------------
FAVIET                    Daniel               dfaviet
SCIARRA                   Ismael               isciarra
CHEN                      John                 jchen
URMAN                     Jose Manuel          jmurman
POPP                      Luis                 lpopp
GREENBERG                 Nancy                ngreenbe

6 rows selected.

See Also:
Oracle Database SQL Language Reference for more information about SQL character functions

Using Datetime Functions in Queries

Datetime functions operate on DATE, time stamp, and interval values. Each datetime function returns a single value for each row that is evaluated. The datetime functions that SQL supports are listed and described in Oracle Database SQL Language Reference.

For each DATE and time stamp value, Oracle Database Express Edition stores this information:

- Year

- Month

- Date

- Hour

- Minute

- Second
For each time stamp value, Oracle Database Express Edition also stores the fractional part of the second, whose precision you can specify. To store the time zone also, use the data type TIMESTAMP WITH TIME ZONE or TIMESTAMP WITH LOCAL TIME ZONE.

For more information about the DATE data type, see Oracle Database SQL Language Reference.

For more information about the TIMESTAMP data type, see Oracle Database SQL Language Reference.

For information about the other time stamp data types and the interval data types, see Oracle Database SQL Language Reference.

The query in Example 2-18 uses the EXTRACT and SYSDATE functions to show how many years each employee in department 100 has been employed. The SYSDATE function returns the current date of the system clock as a DATE value. For more information about the SYSDATE function, see Oracle Database SQL Language Reference. For information about the EXTRACT function, see Oracle Database SQL Language Reference.

Example 2-18 Displaying the Number of Years Between Dates

SELECT LAST_NAME,
(EXTRACT(YEAR FROM SYSDATE) - EXTRACT(YEAR FROM HIRE_DATE)) "Years Employed"
FROM EMPLOYEES
WHERE DEPARTMENT_ID = 100
ORDER BY "Years Employed";

Result:

LAST_NAME                 Years Employed
------------------------- --------------
Popp                                   5
Urman                                  6
Chen                                   7
Sciarra                                7
Greenberg                             10
Faviet                                10

6 rows selected.

The query in Example 2-19 uses the SYSTIMESTAMP function to display the current system date and time. The SYSTIMESTAMP function returns a TIMESTAMP value. For information about the SYSTIMESTAMP function, see Oracle Database SQL Language Reference.

The table in the FROM clause of the query, DUAL, is a one-row table that Oracle Database Express Edition creates automatically along with the data dictionary. Select from DUAL when you want to compute a constant expression with the SELECT statement. Because DUAL has only one row, the constant is returned only once. For more information about selecting from DUAL, see Oracle Database SQL Language Reference.

Example 2-19 Displaying System Date and Time

SELECT EXTRACT(HOUR FROM SYSTIMESTAMP) || ':' ||
EXTRACT(MINUTE FROM SYSTIMESTAMP) || ':' ||
ROUND(EXTRACT(SECOND FROM SYSTIMESTAMP), 0) || ', ' ||
EXTRACT(MONTH FROM SYSTIMESTAMP) || '/' ||
EXTRACT(DAY FROM SYSTIMESTAMP) || '/' ||
EXTRACT(YEAR FROM SYSTIMESTAMP) "System Time and Date"
FROM DUAL;

Results depend on current SYSTIMESTAMP value, but have this format:

System Time and Date
-------------------------------------------------------------------
18:17:53, 12/27/2012

See Also:
Oracle Database SQL Language Reference for more information about SQL datetime functions

Using Conversion Functions in Queries

Conversion functions convert one data type to another. The conversion functions that SQL supports are listed and described in Oracle Database SQL Language Reference.

The query in Example 2-20 uses the TO_CHAR function to convert HIRE_DATE values (which are of type DATE) to character values that have the format FMMonth DD YYYY. FM removes leading and trailing blanks from the month name. FMMonth DD YYYY is an example of a datetime format model. For information about datetime format models, see Oracle Database SQL Language Reference.

Example 2-20 Converting Dates to Characters Using a Format Template

SELECT LAST_NAME,
HIRE_DATE,
TO_CHAR(HIRE_DATE, 'FMMonth DD YYYY') "Date Started"
FROM EMPLOYEES
WHERE DEPARTMENT_ID = 100
ORDER BY LAST_NAME;

Result:

LAST_NAME                 HIRE_DATE Date Started
------------------------- --------- -----------------
Chen                      28-SEP-05 September 28 2005
Faviet                    16-AUG-02 August 16 2002
Greenberg                 17-AUG-02 August 17 2002
Popp                      07-DEC-07 December 7 2007
Sciarra                   30-SEP-05 September 30 2005
Urman                     07-MAR-06 March 7 2006

6 rows selected.

The query in Example 2-21 uses the TO_NUMBER function to convert POSTAL_CODE values (which are of type VARCHAR2) to values of type NUMBER, which it uses in calculations.

Example 2-21 Converting Characters to Numbers

SELECT CITY,
POSTAL_CODE "Old Code",
TO_NUMBER(POSTAL_CODE) + 1 "New Code"
FROM LOCATIONS
WHERE COUNTRY_ID = 'US'
ORDER BY POSTAL_CODE;

Result:

CITY                           Old Code       New Code
------------------------------ ------------ ----------
Southlake                      26192             26193
South Brunswick                50090             50091
Seattle                        98199             98200
South San Francisco            99236             99237

4 rows selected.

See Also:

- Oracle Database SQL Language Reference for more information about SQL conversion functions

- "About the NLS_DATE_FORMAT Parameter"

Using Aggregate Functions in Queries

An aggregate function takes a group of rows and returns a single result row. The group of rows can be an entire table or view. The aggregate functions that SQL supports are listed and described in Oracle Database SQL Language Reference.

Aggregate functions are especially powerful when used with the GROUP BY clause, which groups query results by one or more columns, with a result for each group.

The query in Example 2-22 uses the COUNT function and the GROUP BY clause to show how many people report to each manager. The wildcard character, *, represents an entire record.

Example 2-22 Counting the Number of Rows in Each Group

SELECT MANAGER_ID "Manager",
COUNT(*) "Number of Reports"
FROM EMPLOYEES
GROUP BY MANAGER_ID
ORDER BY MANAGER_ID;

Result:

Manager Number of Reports
---------- -----------------
100                14
101                 5
102                 1
103                 4
108                 5
114                 5
120                 8
121                 8
122                 8
123                 8
124                 8
145                 6
146                 6
147                 6
148                 6
149                 6
201                 1
205                 1
1

19 rows selected.

Example 2-22 shows that one employee does not report to a manager. The following query selects the first name, last name, and job title of that employee:

COLUMN FIRST_NAME FORMAT A10;
COLUMN LAST_NAME FORMAT A10;
COLUMN JOB_TITLE FORMAT A10;

SELECT e.FIRST_NAME,
e.LAST_NAME,
j.JOB_TITLE
FROM EMPLOYEES e, JOBS j
WHERE e.JOB_ID = j.JOB_ID
AND MANAGER_ID IS NULL;

Result:

FIRST_NAME LAST_NAME  JOB_TITLE
---------- ---------- ----------
Steven     King       President

To have the query return only rows where aggregate values meet specified conditions, use an aggregate function in the HAVING clause of the query.

The query in Example 2-23 shows how much each department spends annually on salaries, but only for departments for which that amount exceeds $1,000,000.

Example 2-23 Limiting Aggregate Functions to Rows that Satisfy a Condition

SELECT DEPARTMENT_ID "Department",
SUM(SALARY*12) "All Salaries"
FROM EMPLOYEES
HAVING SUM(SALARY * 12) >= 1000000
GROUP BY DEPARTMENT_ID;

Result:

Department All Salaries
---------- ------------
50      1876800
80      3654000

The query in Example 2-24 uses several aggregate functions to show statistics for the salaries of each JOB_ID.

Example 2-24 Using Aggregate Functions for Statistical Information

SELECT JOB_ID,
COUNT(*) "#",
MIN(SALARY) "Minimum",
ROUND(AVG(SALARY), 0) "Average",
MEDIAN(SALARY) "Median",
MAX(SALARY) "Maximum",
ROUND(STDDEV(SALARY)) "Std Dev"
FROM EMPLOYEES
GROUP BY JOB_ID
ORDER BY JOB_ID;

Result:

JOB_ID              #    Minimum    Average     Median    Maximum    Std Dev
---------- ---------- ---------- ---------- ---------- ---------- ----------
AC_ACCOUNT          1       8300       8300       8300       8300          0
AC_MGR              1      12008      12008      12008      12008          0
AD_ASST             1       4400       4400       4400       4400          0
AD_PRES             1      24000      24000      24000      24000          0
AD_VP               2      17000      17000      17000      17000          0
FI_ACCOUNT          5       6900       7920       7800       9000        766
FI_MGR              1      12008      12008      12008      12008          0
HR_REP              1       6500       6500       6500       6500          0
IT_PROG             5       4200       5760       4800       9000       1926
MK_MAN              1      13000      13000      13000      13000          0
MK_REP              1       6000       6000       6000       6000          0
PR_REP              1      10000      10000      10000      10000          0
PU_CLERK            5       2500       2780       2800       3100        239
PU_MAN              1      11000      11000      11000      11000          0
SA_MAN              5      10500      12200      12000      14000       1525
SA_REP             30       6100       8350       8200      11500       1524
SH_CLERK           20       2500       3215       3100       4200        548
ST_CLERK           20       2100       2785       2700       3600        453
ST_MAN              5       5800       7280       7900       8200       1066

19 rows selected.

See Also:
Oracle Database SQL Language Reference for more information about SQL aggregate functions

Using NULL-Related Functions in Queries

The NULL-related functions facilitate the handling of NULL values. The NULL-related functions that SQL supports are listed and described in Oracle Database SQL Language Reference.

The query in Example 2-25 returns the last name and commission of the employees whose last names begin with 'B'. If an employee receives no commission (that is, if COMMISSION_PCT is NULL), the NVL function substitutes "Not Applicable" for NULL.

Example 2-25 Substituting a String for a NULL Value

SELECT LAST_NAME,
NVL(TO_CHAR(COMMISSION_PCT), 'Not Applicable') "COMMISSION"
FROM EMPLOYEES
WHERE LAST_NAME LIKE 'B%'
ORDER BY LAST_NAME;

Result:

LAST_NAME                 COMMISSION
------------------------- ----------------------------------------
Baer                      Not Applicable
Baida                     Not Applicable
Banda                     .1
Bates                     .15
Bell                      Not Applicable
Bernstein                 .25
Bissot                    Not Applicable
Bloom                     .2
Bull                      Not Applicable

9 rows selected.

The query in Example 2-26 returns the last name, salary, and income of the employees whose last names begin with 'B', using the NVL2 function: If COMMISSION_PCT is not NULL, the income is the salary plus the commission; if COMMISSION_PCT is NULL, income is only the salary.

Example 2-26 Specifying Different Expressions for NULL and Not NULL Values

SELECT LAST_NAME, SALARY,
NVL2(COMMISSION_PCT, SALARY + (SALARY * COMMISSION_PCT), SALARY) INCOME
FROM EMPLOYEES WHERE LAST_NAME LIKE 'B%'
ORDER BY LAST_NAME;

Result:

LAST_NAME                     SALARY     INCOME
------------------------- ---------- ----------
Baer                           10000      10000
Baida                           2900       2900
Banda                           6200       6820
Bates                           7300       8395
Bell                            4000       4000
Bernstein                       9500      11875
Bissot                          3300       3300
Bloom                          10000      12000
Bull                            4100       4100

9 rows selected.

See Also:

- Oracle Database SQL Language Reference for more information about the NVL function

- Oracle Database SQL Language Reference for more information about the NVL2 function

Using CASE Expressions in Queries

A CASE expression lets you use IF ... THEN ... ELSE logic in SQL statements without invoking subprograms. There are two kinds of CASE expressions, simple and searched.

The query in Example 2-27 uses a simple CASE expression to show the country name for each country code.

Example 2-27 Using a Simple CASE Expression in a Query

SELECT UNIQUE COUNTRY_ID ID,
CASE COUNTRY_ID
WHEN 'AU' THEN 'Australia'
WHEN 'BR' THEN 'Brazil'
WHEN 'CA' THEN 'Canada'
WHEN 'CH' THEN 'Switzerland'
WHEN 'CN' THEN 'China'
WHEN 'DE' THEN 'Germany'
WHEN 'IN' THEN 'India'
WHEN 'IT' THEN 'Italy'
WHEN 'JP' THEN 'Japan'
WHEN 'MX' THEN 'Mexico'
WHEN 'NL' THEN 'Netherlands'
WHEN 'SG' THEN 'Singapore'
WHEN 'UK' THEN 'United Kingdom'
WHEN 'US' THEN 'United States'
ELSE 'Unknown'
END COUNTRY
FROM LOCATIONS
ORDER BY COUNTRY_ID;

Result:

ID COUNTRY
-- --------------
AU Australia
BR Brazil
CA Canada
CH Switzerland
CN China
DE Germany
IN India
IT Italy
JP Japan
MX Mexico
NL Netherlands
SG Singapore
UK United Kingdom
US United States

14 rows selected.

The query in Example 2-28 uses a searched CASE expression to show proposed salary increases, based on length of service.

Example 2-28 Using a Searched CASE Expression in a Query

SELECT LAST_NAME "Name",
HIRE_DATE "Started",
SALARY "Salary",
CASE
WHEN HIRE_DATE < TO_DATE('01-Jan-90', 'dd-mon-yy')
THEN TRUNC(SALARY*1.15, 0)
WHEN HIRE_DATE < TO_DATE('01-Jan-95', 'dd-mon-yy')
THEN TRUNC(SALARY*1.10, 0)
WHEN HIRE_DATE < TO_DATE('01-Jan-00', 'dd-mon-yy')
THEN TRUNC(SALARY*1.05, 0)
ELSE SALARY
END "Proposed Salary"
FROM EMPLOYEES
WHERE DEPARTMENT_ID = 100
ORDER BY HIRE_DATE;

Result:

Name                      Started       Salary Proposed Salary
------------------------- --------- ---------- ---------------
Faviet                    16-AUG-02       9000           10350
Greenberg                 17-AUG-02      12008           13809
Chen                      28-SEP-05       8200            9430
Sciarra                   30-SEP-05       7700            8855
Urman                     07-MAR-06       7800            8970
Popp                      07-DEC-07       6900            7935

6 rows selected.

See Also:

- Oracle Database SQL Language Reference for more information about CASE expressions

- Oracle Database PL/SQL Language Reference for more information about CASE expressions

- "Using the DECODE Function in Queries"

- "Using the CASE Statement"

Using the DECODE Function in Queries

The DECODE function compares an expression to several search values. Whenever the value of the expression matches a search value, DECODE returns the result associated with that search value. If DECODE finds no match, then it returns the default value (if specified) or NULL (if no default value is specified).

The query in Example 2-29 uses the DECODE function to show proposed salary increases for three different jobs. The expression is JOB_ID; the search values are 'PU_CLERK', 'SH_CLERK', and 'ST_CLERK'; and the default is SALARY.

Example 2-29 Using the DECODE Function in a Query

SELECT LAST_NAME, JOB_ID, SALARY,
DECODE(JOB_ID,
'PU_CLERK', SALARY * 1.10,
'SH_CLERK', SALARY * 1.15,
'ST_CLERK', SALARY * 1.20,
SALARY) "Proposed Salary"
FROM EMPLOYEES
WHERE JOB_ID LIKE '%_CLERK'
AND LAST_NAME < 'E'
ORDER BY LAST_NAME;

Result:

LAST_NAME                 JOB_ID         SALARY Proposed Salary
------------------------- ---------- ---------- ---------------
Atkinson                  ST_CLERK         2800            3360
Baida                     PU_CLERK         2900            3190
Bell                      SH_CLERK         4000            4600
Bissot                    ST_CLERK         3300            3960
Bull                      SH_CLERK         4100            4715
Cabrio                    SH_CLERK         3000            3450
Chung                     SH_CLERK         3800            4370
Colmenares                PU_CLERK         2500            2750
Davies                    ST_CLERK         3100            3720
Dellinger                 SH_CLERK         3400            3910
Dilly                     SH_CLERK         3600            4140

11 rows selected.

Note:
The arguments of the DECODE function can be any of the SQL numeric or character types. Oracle automatically converts the expression and each search value to the data type of the first search value before comparing. Oracle automatically converts the return value to the same data type as the first result. If the first result has the data type CHAR or if the first result is NULL, then Oracle converts the return value to the data type VARCHAR2.

See Also:

- Oracle Database SQL Language Reference for information about the DECODE function

- "Using CASE Expressions in Queries"

3 About DML Statements and Transactions

This chapter contains:

- About Data Manipulation Language (DML) Statements

- About Transaction Control Statements

- Committing Transactions

- Rolling Back Transactions

- Setting Savepoints in Transactions

About Data Manipulation Language (DML) Statements

Data manipulation language (DML) statements access and manipulate data in existing tables.

In the SQL*Plus environment, you can enter a DML statement after the SQL> prompt.

In the SQL Developer environment, you can enter a DML statement in the Worksheet. Alternatively, you can use the SQL Developer Connections frame and tools to access and manipulate data.

To see the effect of a DML statement in SQL Developer, you might have to select the schema object type of the changed object in the Connections frame and then click the Refresh icon.

The effect of a DML statement is not permanent until you commit the transaction that includes it. A transaction is a sequence of SQL statements that Oracle Database Express Edition treats as a unit (it can be a single DML statement). Until a transaction is committed, it can be rolled back (undone). For more information about transactions, see "About Transaction Control Statements".

This section contains:

- About the INSERT Statement

- About the UPDATE Statement

- About the DELETE Statement

See Also:
Oracle Database SQL Language Reference for more information about DML statements

About the INSERT Statement

The INSERT statement inserts rows into an existing table.

The simplest recommended form of the INSERT statement has this syntax:

INSERT INTO table_name (list_of_columns)
VALUES (list_of_values);

Every column in list_of_columns must have a valid value in the corresponding position in list_of_values. Therefore, before you insert a row into a table, you must know what columns the table has, and what their valid values are. To get this information using SQL Developer, see "Tutorial: Viewing EMPLOYEES Table Properties and Data with SQL Developer". To get this information using SQL*Plus, use the DESCRIBE statement. For example:

DESCRIBE EMPLOYEES;

Result:

Name                                      Null?    Type
----------------------------------------- -------- ------------

EMPLOYEE_ID                               NOT NULL NUMBER(6)
FIRST_NAME                                         VARCHAR2(20)
LAST_NAME                                 NOT NULL VARCHAR2(25)
EMAIL                                     NOT NULL VARCHAR2(25)
PHONE_NUMBER                                       VARCHAR2(20)
HIRE_DATE                                 NOT NULL DATE
JOB_ID                                    NOT NULL VARCHAR2(10)
SALARY                                             NUMBER(8,2)
COMMISSION_PCT                                     NUMBER(2,2)
MANAGER_ID                                         NUMBER(6)
DEPARTMENT_ID                                      NUMBER(4)

The INSERT statement in Example 3-1 inserts a row into the EMPLOYEES table for an employee for which all column values are known.

Example 3-1 Using the INSERT Statement When All Information Is Available

INSERT INTO EMPLOYEES (
EMPLOYEE_ID,
FIRST_NAME,
LAST_NAME,
EMAIL,
PHONE_NUMBER,
HIRE_DATE,
JOB_ID,
SALARY,
COMMISSION_PCT,
MANAGER_ID,
DEPARTMENT_ID
)
VALUES (
10,              -- EMPLOYEE_ID
'George',        -- FIRST_NAME
'Gordon',        -- LAST_NAME
'GGORDON',       -- EMAIL
'650.506.2222',  -- PHONE_NUMBER
'01-JAN-07',     -- HIRE_DATE
'SA_REP',        -- JOB_ID
9000,            -- SALARY
.1,              -- COMMISSION_PCT
148,             -- MANAGER_ID
80               -- DEPARTMENT_ID
);

Result:

1 row created.

You need not know all column values to insert a row into a table, but you must know the values of all NOT NULL columns. If you do not know the value of a column that can be NULL, you can omit that column from list_of_columns. Its value defaults to NULL.

The INSERT statement in Example 3-2 inserts a row into the EMPLOYEES table for an employee for which all column values are known except SALARY. For now, SALARY can have the value NULL. When you know the salary, you can change it with the UPDATE statement (see Example 3-4).

Example 3-2 Using the INSERT Statement When Not All Information Is Available

INSERT INTO EMPLOYEES (
EMPLOYEE_ID,
FIRST_NAME,
LAST_NAME,
EMAIL,
PHONE_NUMBER,
HIRE_DATE,
JOB_ID,          -- Omit SALARY; its value defaults to NULL.
COMMISSION_PCT,
MANAGER_ID,
DEPARTMENT_ID
)
VALUES (
20,              -- EMPLOYEE_ID
'John',          -- FIRST_NAME
'Keats',         -- LAST_NAME
'JKEATS',        -- EMAIL
'650.506.3333',  -- PHONE_NUMBER
'01-JAN-07',     -- HIRE_DATE
'SA_REP',        -- JOB_ID
.1,              -- COMMISSION_PCT
148,             -- MANAGER_ID
80               -- DEPARTMENT_ID
);

Result:

1 row created.

The INSERT statement in Example 3-3 tries to insert a row into the EMPLOYEES table for an employee for which LAST_NAME is not known.

Example 3-3 Using the INSERT Statement Incorrectly

INSERT INTO EMPLOYEES (
EMPLOYEE_ID,
FIRST_NAME,      -- Omit LAST_NAME (error)
EMAIL,
PHONE_NUMBER,
HIRE_DATE,
JOB_ID,
COMMISSION_PCT,
MANAGER_ID,
DEPARTMENT_ID
)
VALUES (
20,              -- EMPLOYEE_ID
'John',          -- FIRST_NAME
'JOHN',          -- EMAIL
'650.506.3333',  -- PHONE_NUMBER
'01-JAN-07',     -- HIRE_DATE
'SA_REP',        -- JOB_ID
.1,              -- COMMISSION_PCT
148,             -- MANAGER_ID
80               -- DEPARTMENT_ID
);

Result:

ORA-01400: cannot insert NULL into ("HR"."EMPLOYEES"."LAST_NAME")

See Also:

- Oracle Database SQL Language Reference for information about the INSERT statement

- Oracle Database SQL Language Reference for information about data types

- "Tutorial: Adding Rows to Tables with the Insert Row Tool"

About the UPDATE Statement

The UPDATE statement updates (changes the values of) a set of existing table rows.

A simple form of the UPDATE statement has this syntax:

UPDATE table_name
SET column_name = value [, column_name = value]...
[ WHERE condition ];

Each value must be valid for its column_name. If you include the WHERE clause, the statement updates column values only in rows that satisfy condition.

SQL DeveloperSQL*Plus
The UPDATE statement in Example 3-4 updates the value of the SALARY column in the row that was inserted into the EMPLOYEES table in Example 3-2, before the salary of the employee was known.

Example 3-4 Using the UPDATE Statement to Add Data

UPDATE EMPLOYEES
SET SALARY = 8500
WHERE LAST_NAME = 'Keats';

Result:

1 row updated.

The UPDATE statement in Example 3-5 updates the commission percentage for every employee in department 80.

Example 3-5 Using the UPDATE Statement to Update Multiple Rows

UPDATE EMPLOYEES
SET COMMISSION_PCT = COMMISSION_PCT + 0.05
WHERE DEPARTMENT_ID = 80;

Result:

34 rows updated.

See Also:

- Oracle Database SQL Language Reference for information about the UPDATE statement

- Oracle Database SQL Language Reference for information about data types

- "Tutorial: Changing Data in Tables in the Data Pane"

About the DELETE Statement

The DELETE statement deletes rows from a table.

A simple form of the DELETE statement has this syntax:

DELETE FROM table_name
[ WHERE condition ];

If you include the WHERE clause, the statement deletes only rows that satisfy condition. If you omit the WHERE clause, the statement deletes all rows from the table, but the empty table still exists. To delete a table, use the DROP TABLE statement.

The DELETE statement in Example 3-6 deletes the rows inserted in Example 3-1 and Example 3-2.

Example 3-6 Using the DELETE Statement

DELETE FROM EMPLOYEES
WHERE HIRE_DATE = TO_DATE('01-JAN-07', 'dd-mon-yy');

Result:

2 rows deleted.

See Also:

- Oracle Database SQL Language Reference for information about the DELETE statement

- Oracle Database SQL Language Reference for information about the DROP TABLE statement

- "Tutorial: Deleting Rows from Tables with the Delete Selected Row(s) Tool"

About Transaction Control Statements

A transaction is a sequence of one or more SQL statements that Oracle Database Express Edition treats as a unit: either all of the statements are performed, or none of them are.

You need transactions to model business processes that require that several operations be performed as a unit. For example, when a manager leaves the company, a row must be inserted into the JOB_HISTORY table to show when the manager left, and for every employee who reports to that manager, the value of MANAGER_ID must be updated in the EMPLOYEES table. To model this process in an application, you must group the INSERT and UPDATE statements into a single transaction.

The basic transaction control statements are:

- SAVEPOINT, which marks a savepoint in a transaction—a point to which you can later roll back. Savepoints are optional, and a transaction can have multiple savepoints.

- COMMIT, which ends the current transaction, makes its changes permanent, erases its savepoints, and releases its locks.

- ROLLBACK, which rolls back (undoes) either the entire current transaction or only the changes made after the specified savepoint.

In the SQL*Plus environment, you can enter a transaction control statement after the SQL> prompt.

In the SQL Developer environment, you can enter a transaction control statement in the Worksheet. SQL Developer also has Commit Changes and Rollback Changes icons, which are explained in "Committing Transactions" and "Rolling Back Transactions".

Caution:
If you do not explicitly commit a transaction, and the program terminates abnormally, then the database automatically rolls back the last uncommitted transaction.
Oracle recommends that you explicitly end transactions in application programs, by either committing them or rolling them back.

See Also:

- Oracle Database Concepts for more information about transaction management

- Oracle Database SQL Language Reference for more information about transaction control statements

Committing Transactions

Committing a transaction makes its changes permanent, erases its savepoints, and releases its locks.

To explicitly commit a transaction, use either the COMMIT statement or (in the SQL Developer environment) the Commit Changes icon.

Note:
Oracle Database Express Edition issues an implicit COMMIT statement before and after any data definition language (DDL) statement. For information about DDL statements, see "About Data Definition Language (DDL) Statements".

Before you commit a transaction:

- Your changes are visible to you, but not to other users of the database instance.

- Your changes are not final—you can undo them with a ROLLBACK statement.

After you commit a transaction:

- Your changes are visible to other users, and to their statements that run after you commit your transaction.

- Your changes are final—you cannot undo them with a ROLLBACK statement.

Example 3-7 adds one row to the REGIONS table (a very simple transaction), checks the result, and then commits the transaction.

Example 3-7 Committing a Transaction

Before transaction:

SELECT * FROM REGIONS
ORDER BY REGION_ID;

Result:

REGION_ID REGION_NAME
---------- -------------------------
1 Europe
2 Americas
3 Asia
4 Middle East and Africa

4 rows selected.

Transaction (add row to table):

INSERT INTO regions (region_id, region_name) VALUES (5, 'Africa');

Result:

1 row created.

Check that row was added:

SELECT * FROM REGIONS
ORDER BY REGION_ID;

Result:

REGION_ID REGION_NAME
---------- -------------------------
1 Europe
2 Americas
3 Asia
4 Middle East and Africa
5 Africa

5 rows selected.

Commit transaction:

COMMIT;

Result:

Commit complete.

See Also:
Oracle Database SQL Language Reference for information about the COMMIT statement

Rolling Back Transactions

Rolling back a transaction undoes its changes. You can roll back the entire current transaction, or you can roll it back only to a specified savepoint.

To roll back the current transaction only to a specified savepoint, you must use the ROLLBACK statement with the TO SAVEPOINT clause.

To roll back the entire current transaction, use either the ROLLBACK statement without the TO SAVEPOINT clause, or (in the SQL Developer environment) the Rollback Changes icon.

Rolling back the entire current transaction:

- Ends the transaction

- Reverses all of its changes

- Erases all of its savepoints

- Releases any transaction locks

Rolling back the current transaction only to the specified savepoint:

- Does not end the transaction

- Reverses only the changes made after the specified savepoint

- Erases only the savepoints set after the specified savepoint (excluding the specified savepoint itself)

- Releases all table and row locks acquired after the specified savepoint
Other transactions that have requested access to rows locked after the specified savepoint must continue to wait until the transaction is either committed or rolled back. Other transactions that have not requested the rows can request and access the rows immediately.

To see the effect of a rollback in SQL Developer, you might have to click the Refresh icon.

As a result of Example 3-7, the REGIONS table has a region called 'Middle East and Africa' and a region called 'Africa'. Example 3-8 corrects this problem (a very simple transaction) and checks the change, but then rolls back the transaction and checks the rollback.

Example 3-8 Rolling Back an Entire Transaction

Before transaction:

SELECT * FROM REGIONS
ORDER BY REGION_ID;

Result:

REGION_ID REGION_NAME
---------- -------------------------
1 Europe
2 Americas
3 Asia
4 Middle East and Africa
5 Africa

5 rows selected.

Transaction (change table):

UPDATE REGIONS
SET REGION_NAME = 'Middle East'
WHERE REGION_NAME = 'Middle East and Africa';

Result:

1 row updated.

Check change:

SELECT * FROM REGIONS
ORDER BY REGION_ID;

Result:

REGION_ID REGION_NAME
---------- -------------------------
1 Europe
2 Americas
3 Asia
4 Middle East
5 Africa

5 rows selected.

Roll back transaction:

ROLLBACK;

Result:

Rollback complete.

Check rollback:

SELECT * FROM REGIONS
ORDER BY REGION_ID;

Result:

REGION_ID REGION_NAME
---------- -------------------------
1 Europe
2 Americas
3 Asia
4 Middle East and Africa
5 Africa

5 rows selected.

See Also:
Oracle Database SQL Language Reference for information about the ROLLBACK statement

Setting Savepoints in Transactions

The SAVEPOINT statement marks a savepoint in a transaction—a point to which you can later roll back. Savepoints are optional, and a transaction can have multiple savepoints.

Example 3-9 does a transaction that includes several DML statements and several savepoints, and then rolls back the transaction to one savepoint, undoing only the changes made after that savepoint.

Example 3-9 Rolling Back a Transaction to a Savepoint

Check REGIONS table before transaction:

SELECT * FROM REGIONS
ORDER BY REGION_ID;

Result:

REGION_ID REGION_NAME
---------- -------------------------
1 Europe
2 Americas
3 Asia
4 Middle East and Africa
5 Africa

5 rows selected.

Check countries in region 4 before transaction:

SELECT COUNTRY_NAME, COUNTRY_ID, REGION_ID
FROM COUNTRIES
WHERE REGION_ID = 4
ORDER BY COUNTRY_NAME;

Result:

COUNTRY_NAME                             CO  REGION_ID
---------------------------------------- -- ----------
Egypt                                    EG          4
Israel                                   IL          4
Kuwait                                   KW          4
Nigeria                                  NG          4
Zambia                                   ZM          4
Zimbabwe                                 ZW          4

6 rows selected.

Check countries in region 5 before transaction:

SELECT COUNTRY_NAME, COUNTRY_ID, REGION_ID
FROM COUNTRIES
WHERE REGION_ID = 5
ORDER BY COUNTRY_NAME;

Result:

no rows selected

Transaction, with several savepoints:

UPDATE REGIONS
SET REGION_NAME = 'Middle East'
WHERE REGION_NAME = 'Middle East and Africa';

UPDATE COUNTRIES
SET REGION_ID = 5
WHERE COUNTRY_ID = 'ZM';
SAVEPOINT zambia;

UPDATE COUNTRIES
SET REGION_ID = 5
WHERE COUNTRY_ID = 'NG';
SAVEPOINT nigeria;

UPDATE COUNTRIES
SET REGION_ID = 5
WHERE COUNTRY_ID = 'ZW';
SAVEPOINT zimbabwe;

UPDATE COUNTRIES
SET REGION_ID = 5
WHERE COUNTRY_ID = 'EG';
SAVEPOINT egypt;

Check REGIONS table after transaction:

SELECT * FROM REGIONS
ORDER BY REGION_ID;

Result:

REGION_ID REGION_NAME
---------- -------------------------
1 Europe
2 Americas
3 Asia
4 Middle East
5 Africa

5 rows selected.

Check countries in region 4 after transaction:

SELECT COUNTRY_NAME, COUNTRY_ID, REGION_ID
FROM COUNTRIES
WHERE REGION_ID = 4
ORDER BY COUNTRY_NAME;

Result:

COUNTRY_NAME                             CO  REGION_ID
---------------------------------------- -- ----------
Israel                                   IL          4
Kuwait                                   KW          4

2 rows selected.

Check countries in region 5 after transaction:

SELECT COUNTRY_NAME, COUNTRY_ID, REGION_ID
FROM COUNTRIES
WHERE REGION_ID = 5
ORDER BY COUNTRY_NAME;

Result:

COUNTRY_NAME                             CO  REGION_ID
---------------------------------------- -- ----------
Egypt                                    EG          5
Nigeria                                  NG          5
Zambia                                   ZM          5
Zimbabwe                                 ZW          5

4 rows selected.

ROLLBACK TO SAVEPOINT nigeria;

Check REGIONS table after rollback:

SELECT * FROM REGIONS
ORDER BY REGION_ID;

Result:

REGION_ID REGION_NAME
---------- -------------------------
1 Europe
2 Americas
3 Asia
4 Middle East
5 Africa

5 rows selected.

Check countries in region 4 after rollback:

SELECT COUNTRY_NAME, COUNTRY_ID, REGION_ID
FROM COUNTRIES
WHERE REGION_ID = 4
ORDER BY COUNTRY_NAME;

Result:

COUNTRY_NAME                             CO  REGION_ID
---------------------------------------- -- ----------
Egypt                                    EG          4
Israel                                   IL          4
Kuwait                                   KW          4
Zimbabwe                                 ZW          4

4 rows selected.

Check countries in region 5 after rollback:

SELECT COUNTRY_NAME, COUNTRY_ID, REGION_ID
FROM COUNTRIES
WHERE REGION_ID = 5
ORDER BY COUNTRY_NAME;

Result:

COUNTRY_NAME                             CO  REGION_ID
---------------------------------------- -- ----------
Nigeria                                  NG          5
Zambia                                   ZM          5

2 rows selected.

See Also:
Oracle Database SQL Language Reference for information about the SAVEPOINT statement

4 Creating and Managing Schema Objects

This chapter contains:

- About Data Definition Language (DDL) Statements

- Creating and Managing Tables

- Creating and Managing Views

- Creating and Managing Sequences

- Creating and Managing Synonyms

About Data Definition Language (DDL) Statements

The statements that create, change, and drop schema objects are data definition language (DDL) statements. Before and after a DDL statement, Oracle Database Express Edition issues an implicit COMMIT statement; therefore, you cannot roll back a DDL statement.

Note:
When creating schema objects, you must observe the schema object naming rules in Oracle Database SQL Language Reference.

In the SQL*Plus environment, you can enter a DDL statement after the SQL> prompt.

In the SQL Developer environment, you can enter a DDL statement in the Worksheet. Alternatively, you can use SQL Developer tools to create, change, and drop objects.

Some DDL statements that create schema objects have an optional OR REPLACE clause, which allows a statement to replace an existing schema object with another that has the same name and type. When SQL Developer generates code for one of these statements, it always includes the OR REPLACE clause.

To see the effect of a DDL statement in SQL Developer, you might have to select the schema object type of the newly created object in the Connections frame and then click the Refresh icon.

See Also:

- Oracle Database SQL Language Reference for more information about DDL statements

- "Committing Transactions"

Creating and Managing Tables

Tables are the basic units of data storage in Oracle Database Express Edition. Tables hold all user-accessible data. Each table contains rows that represent individual data records. Rows are composed of columns that represent the fields of the records.

This section contains:

- About SQL Data Types

- Creating Tables

- Ensuring Data Integrity in Tables

- Tutorial: Adding Rows to Tables with the Insert Row Tool

- Tutorial: Changing Data in Tables in the Data Pane

- Tutorial: Deleting Rows from Tables with the Delete Selected Row(s) Tool

- Managing Indexes

- Dropping Tables

Note:
To do the tutorials in this document, you must be connected to Oracle Database Express Edition as the user HR from SQL Developer.

See Also:

- "Tutorial: Viewing EMPLOYEES Table Properties and Data with SQL Developer"

- Oracle SQL Developer User's Guide for a SQL Developer tutorial that includes creating and populating tables

- Oracle Database Concepts for general information about tables

About SQL Data Types

When you create a table, you must specify the SQL data type for each column. The data type of a column determines what values the column can contain. For example, a column of type DATE can contain the value '01-MAY-05', but it cannot contain the numeric value 2 or the character value 'shoe'. SQL data types fall into two categories: built-in and user-defined. (PL/SQL has additional data types—see "About PL/SQL Data Types".)

See Also:

- Oracle Database SQL Language Reference for a summary of built-in SQL data types

- Oracle Database Concepts for introductions to each of the built-in SQL data types

- Oracle Database SQL Language Reference for more information about user-defined data types

- "About PL/SQL Data Types"

Creating Tables

To create tables, use either the SQL Developer tool Create Table or the DDL statement CREATE TABLE. This section shows how to use both of these ways to create these tables, which will contain data about employee evaluations:

- PERFORMANCE_PARTS, which contains the categories of employee performance that are evaluated and their relative weights

- EVALUATIONS, which contains employee information, evaluation date, job, manager, and department

- SCORES, which contains the scores assigned to each performance category for each evaluation

These tables appear in many tutorials and examples in this document.

This section contains:

- Tutorial: Creating a Table with the Create Table Tool

- Creating Tables with the CREATE TABLE Statement

Tutorial: Creating a Table with the Create Table Tool

This tutorial shows how to create the PERFORMANCE_PARTS table using the Create Table tool.

To create the PERFORMANCE_PARTS table using the Create Table tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, right-click Tables.

3. In the list of choices, click New Table.
The Create Table window opens, with default values for a new table, which has only one row.

4. For Schema, accept the default value, HR.

5. For Name, enter PERFORMANCE_PARTS.

6. In the default row:

- For PK (primary key), accept the default option, deselected.

- For Column Name, enter PERFORMANCE_ID.

- For Type, accept the default value, VARCHAR2.

- For Size, enter 2.

- For Not Null, accept the default option, deselected.

7. Click Add Column.

8. For Column Name, enter NAME.

9. For Type, accept the default value, VARCHAR2.

10. For Size, enter 80.

11. Click Add Column.

12. For Column Name, enter WEIGHT.

13. For Type, select NUMBER from the menu.

14. Click OK.
The table PERFORMANCE_PARTS is created. Its name appears under Tables in the Connections frame.

To see the CREATE TABLE statement for creating this table, select PERFORMANCE_PARTS and click the tab SQL.

See Also:
Oracle SQL Developer User's Guide for more information about using SQL Developer to create tables

Creating Tables with the CREATE TABLE Statement

This section shows how to use the CREATE TABLE statement to create the EVALUATIONS and SCORES tables.

The CREATE TABLE statement in Example 4-1 creates the EVALUATIONS table.

Example 4-1 Creating the EVALUATIONS Table with CREATE TABLE

CREATE TABLE EVALUATIONS (
EVALUATION_ID    NUMBER(8,0),
EMPLOYEE_ID      NUMBER(6,0),
EVALUATION_DATE  DATE,
JOB_ID           VARCHAR2(10),
MANAGER_ID       NUMBER(6,0),
DEPARTMENT_ID    NUMBER(4,0),
TOTAL_SCORE      NUMBER(3,0)
);

Result:

Table created.

The CREATE TABLE statement in Example 4-2 creates the SCORES table.

Example 4-2 Creating the SCORES Table with CREATE TABLE

CREATE TABLE SCORES (
EVALUATION_ID   NUMBER(8,0),
PERFORMANCE_ID  VARCHAR2(2),
SCORE           NUMBER(1,0)
);

Result:

Table created.

In SQL Developer, in the Connections frame, if you expand Tables, you can see the tables EVALUATIONS and SCORES.

See Also:
Oracle Database SQL Language Reference for information about the CREATE TABLE statement

Ensuring Data Integrity in Tables

To ensure that the data in your tables satisfies the business rules that your application models, you can use constraints, application logic, or both.

Constraints restrict the values that columns can have. Trying to change the data in a way that violates a constraint causes an error and rolls back the change. Trying to add a constraint to a populated table causes an error if existing data violates the constraint.

Tip:
Wherever possible, use constraints instead of application logic. Oracle Database Express Edition checks that all data obeys constraints much faster than application logic can.

Constraints can be enabled and disabled. By default, they are created in the enabled state.

This section contains:

- About Constraint Types

- Tutorial: Adding Constraints to Existing Tables

See Also:

- Oracle Database Concepts for additional general information about constraints

- Oracle Database SQL Language Reference for syntactic information about constraints

- Oracle Database Advanced Application Developer's Guide for information about enabling and disabling constraints

- "Deploying the Sample Application"

About Constraint Types

The constraint types are:

- Not Null, which prevents a value from being null
In the EMPLOYEES table, the column LAST_NAME has the NOT NULL constraint, which enforces the business rule that every employee must have a last name.

- Unique, which prevents multiple rows from having the same value in the same column or combination of columns, but allows some values to be null
In the EMPLOYEES table, the column EMAIL has the UNIQUE constraint, which enforces the business rule that an employee can have no email address, but cannot have the same email address as another employee.

- Primary Key, which is a combination of NOT NULL and UNIQUE
In the EMPLOYEES table, the column EMPLOYEE_ID has the PRIMARY KEY constraint, which enforces the business rule that every employee must have a unique employee identification number.

- Foreign Key, which requires values in one table to match values in another table
In the EMPLOYEES table, the column JOB_ID has a FOREIGN KEY constraint that references the JOBS table, which enforces the business rule that an employee cannot have a JOB_ID that is not in the JOBS table.

- Check, which requires that a value satisfy a specified condition
The EMPLOYEES table does not have CHECK constraints. However, suppose that EMPLOYEES needs a new column, EMPLOYEE_AGE, and that every employee must be at least 18. The constraint CHECK (EMPLOYEE_AGE >= 18) enforces the business rule.

Tip:
Use check constraints only when other constraint types cannot provide the necessary checking.

- REF, which further describes the relationship between a REF column and the object that it references
A REF column references an object in another object type or in a relational table.

For information about REF constraints, see Oracle Database Concepts.

See Also:

- Oracle Database Concepts for additional general information about constraint types

- Oracle Database SQL Language Reference for syntactic information about constraints

Tutorial: Adding Constraints to Existing Tables

To add constraints to existing tables, use either SQL Developer tools or the DDL statement ALTER TABLE. This section shows how to use both of these ways to add constraints to the tables created in "Creating Tables".

This tutorial has several procedures. The first procedure uses the Edit Table tool to add a Not Null constraint to the NAMES column of the PERFORMANCE_PARTS table. The remaining procedures show how to use other tools to add constraints; however, you could add the same constraints using the Edit Table tool.

Note:
After any step of the tutorial, you can view the constraints that a table has:

1. In the Connections frame, select the name of the table.

2. In the right frame, click the tab Constraints.

For more information about viewing table properties and data, see "Tutorial: Viewing EMPLOYEES Table Properties and Data with SQL Developer".

To add a Not Null constraint using the Edit Table tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand Tables.

3. In the list of tables, right-click PERFORMANCE_PARTS.

4. In the list of choices, click Edit.

5. In the Edit Table window, click the column NAME.

6. Select the property Not Null.

7. Click OK.
The Not Null constraint is added to the NAME column of the PERFORMANCE_PARTS table.

The following procedure uses the ALTER TABLE statement to add a Not Null constraint to the WEIGHT column of the PERFORMANCE_PARTS table.

To add a Not Null constraint using the ALTER TABLE statement:

1. If a pane with the tab hr_conn is there, select it. Otherwise, click the icon SQL Worksheet, as in "Running Queries in SQL Developer".

2. In the Worksheet pane, type this statement:

ALTER TABLE PERFORMANCE_PARTS
MODIFY WEIGHT NOT NULL;

3. Click the icon Run Statement.
The statement runs, adding the Not Null constraint to the WEIGHT column of the PERFORMANCE_PARTS table.

The following procedure uses the Add Unique tool to add a Unique constraint to the SCORES table.

To add a Unique constraint using the Add Unique tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand Tables.

3. In the list of tables, right-click SCORES.

4. In the list of choices, select Constraint.

5. In the list of choices, click Add Unique.

6. In the Add Unique window:

1. For Constraint Name, enter SCORES_EVAL_PERF_UNIQUE.

2. For Column 1, select EVALUATION_ID from the menu.

3. For Column 2, select PERFORMANCE_ID from the menu.

4. Click Apply.

7. In the Confirmation window, click OK.
A unique constraint named SCORES_EVAL_PERF_UNIQUE is added to the SCORES table.

The following procedure uses the Add Primary Key tool to add a Primary Key constraint to the PERFORMANCE_ID column of the PERFORMANCE_PARTS table.

To add a Primary Key constraint using the Add Primary Key tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand Tables.

3. In the list of tables, right-click PERFORMANCE_PARTS.

4. In the list of choices, select Constraint.

5. In the list of choices, click Add Primary Key.

6. In the Add Primary Key window:

1. For Primary Key Name, enter PERF_PERF_ID_PK.

2. For Column 1, select PERFORMANCE_ID from the menu.

3. Click Apply.

7. In the Confirmation window, click OK.
A primary key constraint named PERF_PERF_ID_PK is added to the PERFORMANCE_ID column of the PERFORMANCE_PARTS table.

The following procedure uses the ALTER TABLE statement to add a Primary Key constraint to the EVALUATION_ID column of the EVALUATIONS table.

To add a Primary Key constraint using the ALTER TABLE statement:

1. If a pane with the tab hr_conn is there, select it. Otherwise, click the icon SQL Worksheet, as in "Running Queries in SQL Developer".

2. In the Worksheet pane, type this statement:

ALTER TABLE EVALUATIONS
ADD CONSTRAINT EVAL_EVAL_ID_PK PRIMARY KEY (EVALUATION_ID);

3. Click the icon Run Statement.
The statement runs, adding the Primary Key constraint to the EVALUATION_ID column of the EVALUATIONS table.

The following procedure uses the Add Foreign Key tool to add two Foreign Key constraints to the SCORES table.

To add two Foreign Key constraints using the Add Foreign Key tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand Tables.

3. In the list of tables, right-click SCORES.

4. In the list of choices, select Constraint.

5. In the list of choices, click Add Foreign Key.

6. In the Add Foreign Key window:

1. For Constraint Name, enter SCORES_EVAL_FK.

2. For Column Name, select EVALUATION_ID from the menu.

3. For References Table Name, select EVALUATIONS from the menu.

4. For Referencing Column, select EVALUATION_ID from the menu.

5. Click Apply.

7. In the Confirmation window, click OK.
A foreign key constraint named SCORES_EVAL_FK is added to the EVALUTION_ID column of the SCORES table, referencing the EVALUTION_ID column of the EVALUATIONS table.

The following steps add another foreign key constraint to the SCORES table.

8. In the list of tables, right-click SCORES.

9. In the list of tables, select Constraint.

10. In the list of choices, click Add Foreign Key.
The Add Foreign Key window opens.

11. In the Add Foreign Key window:

1. For Constraint Name, enter SCORES_PERF_FK.

2. For Column Name, select PERFORMANCE_ID from the menu.

3. For Reference Table Name, select PERFORMANCE_PARTS from the menu.

4. For Referencing Column, select PERFORMANCE_ID from the menu.

5. Click Apply.

12. In the Confirmation window, click OK.
A foreign key constraint named SCORES_PERF_FK is added to the EVALUTION_ID column of the SCORES table, referencing the EVALUTION_ID column of the EVALUATIONS table.

The following procedure uses the ALTER TABLE statement to add a Foreign Key constraint to the EMPLOYEE_ID column of the EVALUATIONS table, referencing the EMPLOYEE_ID column of the EMPLOYEES table.

To add a Foreign Key constraint using the ALTER TABLE statement:

1. If a pane with the tab hr_conn is there, select it. Otherwise, click the icon SQL Worksheet, as in "Running Queries in SQL Developer".

2. In the Worksheet pane, type this statement:

ALTER TABLE EVALUATIONS
ADD CONSTRAINT EVAL_EMP_ID_FK FOREIGN KEY (EMPLOYEE_ID)
REFERENCES EMPLOYEES (EMPLOYEE_ID);

3. Click the icon Run Statement.
The statement runs, adding the Foreign Key constraint to the EMPLOYEE_ID column of the EVALUATIONS table, referencing the EMPLOYEE_ID column of the EMPLOYEES table.

The following procedure uses the Add Check tool to add a Check constraint to the SCORES table.

To add a Check constraint using the Add Check tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand Tables.

3. In the list of tables, right-click SCORES.

4. In the list of choices, select Constraint.

5. In the list of choices, click Add Check.

6. In the Add Check window:

1. For Constraint Name, enter SCORE_VALID.

2. For Check Condition, enter score >= 0 and score <= 9.

3. For Status, accept the default, ENABLE.

4. Click Apply.

7. In the Confirmation window, click OK.
A Check constraint named SCORE_VALID is added to the SCORES table.

See Also:

- Oracle Database SQL Language Reference for more information about the ALTER TABLE statement

- Oracle SQL Developer User's Guide for information about adding constraints to a table when you create it with SQL Developer

- Oracle Database SQL Language Reference for information about adding constraints to a table when you create it with the CREATE TABLE statement

Tutorial: Adding Rows to Tables with the Insert Row Tool

This tutorial shows how to use the Insert Row tool to add six populated rows to the PERFORMANCE_PARTS table.

To add rows to the PERFORMANCE_PARTS table using the Insert Row tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand Tables.

3. In the list of tables, select PERFORMANCE_PARTS.

4. In the right frame, click the tab Data.
The Data pane appears, showing the names of the columns of the PERFORMANCE_PARTS table and no rows.

5. In the Data pane, click the icon Insert Row.

A new row appears, with empty columns. A green border around the row number indicates that the insertion has not been committed.

6. Click the cell under the column heading PERFORMANCE_ID.

7. Type the value of PERFORMANCE_ID: WM

8. Either press the key Tab or click the cell under the column heading NAME.

9. Type the value of NAME: Workload Management

10. Either press the key Tab or click the cell under the column heading WEIGHT.

11. Type the value of WEIGHT: 0.2

12. Press the key Enter.

13. Add and populate a second row by repeating steps 5 through 12 with these values:

- For PERFORMANCE_ID, type BR.

- For NAME, type Building Relationships.

- For WEIGHT, type 0.2.

14. Add and populate a third row by repeating steps 5 through 12 with these values:

- For PERFORMANCE_ID, type CF.

- For NAME, type Customer Focus.

- For WEIGHT, type 0.2.

15. Add and populate a fourth row by repeating steps 5 through 12 with these values:

- For PERFORMANCE_ID, type CM.

- For NAME, type Communication.

- For WEIGHT, type 0.2.

16. Add and populate a fifth row by repeating steps 5 through 12 with these values:

- For PERFORMANCE_ID, type TW.

- For NAME, type Teamwork.

- For WEIGHT, type 0.2.

17. Add and populate a sixth row by repeating steps 5 through 12, using these values:

- For PERFORMANCE_ID, type RO.

- For NAME, type Results Orientation.

- For WEIGHT, type 0.2.

18. Click the icon Commit Changes.
The green borders around the row numbers disappear.

Under the Data pane is the label Messages - Log.

19. Check the Messages - Log pane for the message "Commit Successful".

20. In the Data Pane, check the new rows.

See Also:
"About the INSERT Statement"

Tutorial: Changing Data in Tables in the Data Pane

This tutorial shows how to change three of the WEIGHT values in the PERFORMANCE_PARTS table (populated in "Tutorial: Adding Rows to Tables with the Insert Row Tool") in the Data pane.

To change data in the PERFORMANCE_PARTS table using the Data pane:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand Tables.

3. In the list of tables, select PERFORMANCE_PARTS.

4. In the right frame, click the tab Data.

5. In the Data Pane, in the row where NAME is Workload Management:

1. Click the WEIGHT value.

2. Enter the value 0.3.

3. Press the key Enter.
An asterisk appears to the left of the row number to indicate that the change has not been committed.

6. In the row where NAME is Building Relationships:

1. Click the WEIGHT value.

2. Enter the value 0.15.

3. Press the key Enter.
An asterisk appears to the left of the row number to indicate that the change has not been committed.

7. In the row where NAME is Customer Focus:

1. Click the WEIGHT value.

2. Enter the value 0.15.

3. Press the key Enter.
An asterisk appears to the left of the row number to indicate that the change has not been committed.

8. Click the icon Commit Changes.
The asterisks to the left of the row numbers disappear.

9. Under the Data pane, check the Messages - Log pane for the message "Commit Successful".

10. In the Data Pane, check the new data.

See Also:
"About the UPDATE Statement"

Tutorial: Deleting Rows from Tables with the Delete Selected Row(s) Tool

This tutorial shows how to use the Delete Selected Row(s) tool to delete a row from the PERFORMANCE_PARTS table (populated in "Tutorial: Adding Rows to Tables with the Insert Row Tool").

To delete row from PERFORMANCE_PARTS using Delete Selected Row(s) tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand Tables.

3. In the list of tables, select PERFORMANCE_PARTS.

4. In the right frame, click the tab Data.

5. In the Data pane, click the row where NAME is Results Orientation.

6. Click the icon Delete Selected Row(s).
A red border appears around the row number to indicate that the deletion has not been committed.

7. Click the icon Commit Changes.
The row is deleted.

8. Under the Data pane, check the Messages - Log pane for the message "Commit Successful".

Note:
If you delete every row of a table, the empty table still exists. To delete a table, see "Dropping Tables".

See Also:
"About the DELETE Statement"

Managing Indexes

You can create indexes on one or more columns of a table to speed SQL statement execution on that table. When properly used, indexes are the primary means of reducing disk input/output (I/O).

When you define a primary key on a table:

- If an existing index starts with the primary key columns, then Oracle Database Express Edition uses that existing index for the primary key. The existing index need not be Unique.
For example, if you define the primary key (A, B), Oracle Database Express Edition uses the existing index (A, B, C).

- If no existing index starts with the primary key columns and the constraint is immediate, then Oracle Database Express Edition creates a Unique index on the primary key.

- If no existing index starts with the primary key columns and the constraint is deferrable, then Oracle Database Express Edition creates a non-Unique index on the primary key.

For example, in "Tutorial: Adding Constraints to Existing Tables", you added a Primary Key constraint to the EVALUATION_ID column of the EVALUATIONS table. Therefore, if you select the EVALUATIONS table in the SQL Developer Connections frame and click the Indexes tab, the Indexes pane shows a Unique index on the EVALUATION_ID column.

This section contains:

- Tutorial: Adding an Index with the Create Index Tool

- Tutorial: Changing an Index with the Edit Index Tool

- Tutorial: Dropping an Index

See Also:
For more information about indexes:

- Oracle Database Concepts

- Oracle Database Advanced Application Developer's Guide

Tutorial: Adding an Index with the Create Index Tool

To create an index, use either the SQL Developer tool Create Index or the DDL statement CREATE INDEX.

This tutorial shows how to use the Create Index tool to add an index to the EVALUATIONS table created in Example 4-1. The equivalent DDL statement is:

CREATE INDEX EVAL_JOB_IX
ON EVALUATIONS (JOB_ID ASC) NOPARALLEL;

To add an index to the EVALUATIONS table using the Create Index tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand Tables.

3. In the list of tables, right-click EVALUATIONS.

4. In the list of choices, select Index.

5. In the list of choices, select Create Index.

6. In the Create Index window:

1. For Schema, accept the default, HR.

2. For Name, type EVAL_JOB_IX.

3. If the Definition pane does not show, select the tab Definition.

4. In the Definition pane, for Index Type, select Unique from the menu.

5. Click the icon Add Expression.
The Expression EMPLOYEE_ID with Order <Not Specified> appears.

6. Over EMPLOYEE_ID, type JOB_ID.

7. For Order, select ASC (ascending) from the menu.

8. Click OK.
Now the EVALUATIONS table has an index named EVAL_JOB_IX on the column JOB_ID.

See Also:
Oracle Database SQL Language Reference for information about the CREATE INDEX statement

Tutorial: Changing an Index with the Edit Index Tool

To change an index, use either the SQL Developer tool Edit Index or the DDL statements DROP INDEX and CREATE INDEX.

This tutorial shows how to use the Edit Index tool to reverse the sort order of the index EVAL_JOB_IX. The equivalent DDL statements are:

DROP INDEX EVAL_JOB_ID;

CREATE INDEX EVAL_JOB_IX
ON EVALUATIONS (JOB_ID DESC) NOPARALLEL;

To reverse the sort order of the index EVAL_JOB_IX using the Edit Index tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand Indexes.

3. In the list of indexes, right-click EVAL_JOB_IX.

4. In the list of choices, click Edit.

5. In the Edit Index window, change Order to DESC.

6. Click OK.

7. In the Confirm Replace window, click either Yes or No.

See Also:
Oracle Database SQL Language Reference for information about the ALTER INDEX statement

Tutorial: Dropping an Index

To drop an index, use either the SQL Developer Connections frame and Drop tool or the DDL statement DROP INDEX.

This tutorial shows how to use the Connections frame and Drop tool to drop the index EVAL_JOB_IX. The equivalent DDL statement is:

DROP INDEX EVAL_JOB_ID;

To drop the index EVAL_JOB_IX:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand Indexes.

3. In the list of indexes, right-click EVAL_JOB_IX.

4. In the list of choices, click Drop.

5. In the Drop window, click Apply.

6. In the Confirmation window, click OK.

See Also:
Oracle Database SQL Language Reference for information about the DROP INDEX statement

Dropping Tables

To drop a table, use either the SQL Developer Connections frame and Drop tool, or the DDL statement DROP TABLE.

Caution:
Do not drop any tables that you created in "Creating Tables"—you need them for later tutorials. If you want to practice dropping tables, create simple ones and then drop them.

To drop a table using the Drop tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand Tables.

3. In the list of tables, right-click the name of the table to drop.

4. In the list of choices, select Table.

5. In the list of choices, click Drop.

6. In the Drop window, click Apply.

7. In the Confirmation window, click OK.

See Also:
Oracle Database SQL Language Reference for information about the DROP TABLE statement

Creating and Managing Views

A view presents a query result as a table. In most places that you can use a table, you can use a view. Views are useful when you need frequent access to information that is stored in several different tables.

This section contains:

- Creating Views

- Changing Queries in Views

- Tutorial: Changing View Names with the Rename Tool

- Dropping Views

See Also:

- "Selecting Table Data" for information about queries

- Oracle Database Concepts for additional general information about views

Creating Views

To create views, use either the SQL Developer tool Create View or the DDL statement CREATE VIEW. This section shows how to use both of these ways to create these views:

- SALESFORCE, which contains the names and salaries of the employees in the Sales department

- EMP_LOCATIONS, which contains the names and locations of all employees
This view is used in "Creating an INSTEAD OF Trigger".

This section contains:

- Tutorial: Creating a View with the Create View Tool

- Creating Views with the CREATE VIEW Statement

See Also:

- Oracle SQL Developer User's Guide for more information about using SQL Developer to create a view

- Oracle Database SQL Language Reference for more information about the CREATE VIEW statement

Tutorial: Creating a View with the Create View Tool

This tutorial shows how to create the SALESFORCE view using the Create View tool.

To create the SALESFORCE view using the Create View tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, right-click Views.

3. In the list of choices, click New View.
The Create View window opens, with default values for a new view.

4. For Schema, accept the default value, HR.

5. For Name, enter SALESFORCE.

6. If the SQL Query pane does not show, click the tab SQL Query.

7. In the SQL Query pane, in the SQL Query field:

- After SELECT, type:

FIRST_NAME || ' ' || LAST_NAME "Name", SALARY*12 "Annual Salary"

- After FROM, type:

EMPLOYEES WHERE DEPARTMENT_ID = 80

8. Click Check Syntax.

9. Under "Syntax Results," if the message is not "No errors found in SQL", then return to step 7 and correct the syntax errors in the query.

10. Click OK.
The view SALESFORCE is created. To see it, expand Views in the Connections frame.

To see the CREATE VIEW statement for creating this view, select its name and click the tab SQL.

See Also:
Oracle SQL Developer User's Guide for more information about using SQL Developer to create views

Creating Views with the CREATE VIEW Statement

The CREATE VIEW statement in Example 4-3 creates the EMP_LOCATIONS view, which joins four tables. (For information about joins, see "Selecting Data from Multiple Tables".)

Example 4-3 Creating the EMP_LOCATIONS View with CREATE VIEW

CREATE VIEW EMP_LOCATIONS AS
SELECT e.EMPLOYEE_ID,
e.LAST_NAME || ', ' || e.FIRST_NAME NAME,
d.DEPARTMENT_NAME DEPARTMENT,
l.CITY CITY,
c.COUNTRY_NAME COUNTRY
FROM EMPLOYEES e, DEPARTMENTS d, LOCATIONS l, COUNTRIES c
WHERE e.DEPARTMENT_ID = d.DEPARTMENT_ID AND
d.LOCATION_ID = l.LOCATION_ID AND
l.COUNTRY_ID = c.COUNTRY_ID
ORDER BY LAST_NAME;

Result:

View EMP_LOCATIONS created.

See Also:
Oracle Database SQL Language Reference for information about the CREATE VIEW statement

Changing Queries in Views

To change the query in a view, use the DDL statement CREATE VIEW with the OR REPLACE clause.

The CREATE OR REPLACE VIEW statement in Example 4-4 changes the query in the SALESFORCE view.

Example 4-4 Changing the Query in the SALESFORCE View

CREATE OR REPLACE VIEW SALESFORCE AS
SELECT FIRST_NAME || ' ' || LAST_NAME "Name",
SALARY*12 "Annual Salary"
FROM EMPLOYEES
WHERE DEPARTMENT_ID = 80 OR DEPARTMENT_ID = 20;

Result:

View SALESFORCE created.

See Also:
Oracle Database SQL Language Reference for information about the CREATE VIEW statement with the OR REPLACE clause

Tutorial: Changing View Names with the Rename Tool

To change the name of a view, use either the SQL Developer tool Rename or the RENAME statement.

This tutorial shows how to use the Rename tool to change the name of the SALESFORCE view. The equivalent DDL statement is:

RENAME SALESFORCE to SALES_MARKETING;

To change the SALESFORCE view using the Rename tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand Views.

3. In the list of views, right-click SALESFORCE.

4. In the list of choices, select Rename.

5. In the Rename window, in the New View Name field, type SALES_MARKETING.

6. Click Apply.

7. In the Confirmation window, click OK.

See Also:
Oracle Database SQL Language Reference for information about the RENAME statement

Dropping Views

To drop a view, use either the SQL Developer Connections frame and Drop tool or the DDL statement DROP VIEW.

This tutorial shows how to use the Connections frame and Drop tool to drop the view SALES_MARKETING (changed in "Tutorial: Changing View Names with the Rename Tool"). The equivalent DDL statement is:

DROP VIEW SALES_MARKETING;

To drop the view SALES_MARKETING using the Drop tool:

1. In the Connections frame, expand hr_conn.

2. In the a list of schema object types, expand Views.

3. In the a list of views, right-click SALES_MARKETING.

4. In the a list of choices, click Drop.

5. In the Drop window, click Apply.

6. In the Confirmation window, click OK.

See Also:
Oracle Database SQL Language Reference for information about the DROP VIEW statement

Creating and Managing Sequences

Sequences are schema objects from which you can generate unique sequential values, which are very useful when you need unique primary keys. The HR schema has three sequences: DEPARTMENTS_SEQUENCE, EMPLOYEES_SEQUENCE, and LOCATIONS_SEQUENCE.

Sequences are used through the pseudocolumns CURRVAL and NEXTVAL, which return the current and next values of the sequence, respectively. After creating a sequence, you must initialize it by using NEXTVAL to get its first value. Only after you initialize a sequence does CURRVAL return its current value.

Tip:
When you plan to use a sequence to populate the primary key of a table, give the sequence a name that reflects this purpose. (This section uses the naming convention TABLE_NAME_SEQUENCE.)

This section contains:

- Tutorial: Creating a Sequence

- Dropping Sequences

See Also:

- Oracle Database Concepts for information about the sequence generator

- Oracle Database SQL Language Reference for more information about the CURRVAL and NEXTVAL pseudocolumns

- Oracle Database Administrator's Guide for information about managing sequences

- "Editing Installation Scripts that Create Sequences"

- "About Sequences and Concurrency"

Tutorial: Creating a Sequence

To create a sequence, use either the SQL Developer tool Create Sequence or the DDL statement CREATE SEQUENCE.

This tutorial shows how to use the Create Database Sequence tool to create a sequence to use to generate primary keys for the EVALUATIONS table created in Example 4-1. The equivalent DDL statement is:

CREATE SEQUENCE evaluations_sequence
INCREMENT BY 1
START WITH 1 ORDER;

To create EVALUATIONS_SEQUENCE using the Create Database Sequence tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, right-click Sequences.

3. In the list of choices, click New Sequence.

4. In the Create Sequence window, in the Name field, type EVALUATIONS_SEQUENCE over the default value SEQUENCE1.

5. If the Properties pane does not show, click the tab Properties.

6. In the Properties pane:

1. In the field Increment, type 1.

2. In the field Start with, type 1.

3. For the remaining fields, accept the default values.

4. Click OK.
The sequence EVALUATIONS_SEQUENCE is created. Its name appears under Sequences in the Connections frame.

See Also:

- Oracle SQL Developer User's Guide for more information about using SQL Developer to create a sequence

- Oracle Database SQL Language Reference for information about the CREATE SEQUENCE statement

- "Tutorial: Creating a Trigger that Generates a Primary Key for a Row Before It Is Inserted" to learn how to create a trigger that inserts the primary keys created by EVALUATIONS_SEQUENCE into the EVALUATIONS table

Dropping Sequences

To drop a sequence, use either the SQL Developer Connections frame and Drop tool, or the DDL statement DROP SEQUENCE.

This statement drops the sequence EVALUATIONS_SEQUENCE:

DROP SEQUENCE EVALUATIONS_SEQUENCE;

Caution:
Do not drop the sequence EVALUATIONS_SEQUENCE—you need them for Example 5-3. If you want to practice dropping sequences, create others and then drop them.

To drop a sequence using the Drop tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand Sequences.

3. In the list of sequences, right-click the name of the sequence to drop.

4. In the list of choices, click Drop.

5. In the Drop window, click Apply.

6. In the Confirmation window, click OK.

See Also:
Oracle Database SQL Language Reference for information about the DROP SEQUENCE statement

Creating and Managing Synonyms

A synonym is an alias for another schema object. Some reasons to use synonyms are security (for example, to hide the owner and location of an object) and convenience. Examples of convenience are:

- Using a short synonym, such as SALES, for a long object name, such as ACME_CO.SALES_DATA

- Using a synonym for a renamed object, instead of changing that object name throughout the applications that use it
For example, if your application uses a table named DEPARTMENTS, and its name changes to DIVISIONS, you can create a DEPARTMENTS synonym for that table and continue to reference it by its original name.

This section contains:

- Creating Synonyms

- Dropping Synonyms

See Also:
Oracle Database Concepts for additional general information about synonyms

Creating Synonyms

To create a synonym, use either the SQL Developer tool Create Database Synonym or the DDL statement CREATE SYNONYM.

This tutorial shows how to use the Create Database Synonym tool to create the synonym EMP for the EMPLOYEES table. The equivalent DDL statement is:

CREATE SYNONYM EMPL FOR EMPLOYEES;

To create the synonym EMP using the Create Database Synonym tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, right-click Synonyms.

3. In the list of choices, click New Synonym.

4. In the New Synonym window:

1. In the Synonym Name field, type EMPL.

2. In the Object Owner field, select HR from the menu.

3. In the Object Name field, select EMPLOYEES from the menu.
The synonym refers to a specific schema object; in this case, the table EMPLOYEES.

4. Click Apply.

5. In the Confirmation window, click OK.
The synonym EMPL is created. To see it, expand Synonyms in the Connections frame. You can now use EMPL instead of EMPLOYEES.

See Also:
Oracle Database SQL Language Reference for information about the CREATE SYNONYM statement

Dropping Synonyms

To drop a synonym, use either the SQL Developer Connections frame and Drop tool, or the DDL statement DROP SYNONYM.

This statement drops the synonym EMP:

DROP SYNONYM EMP;

To drop a synonym using the Drop tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand Synonyms.

3. In the list of synonyms, right-click the name of the synonym to drop.

4. In the list of choices, click Drop.

5. In the Drop window, click Apply.

6. In the Confirmation window, click OK.

See Also:
Oracle Database SQL Language Reference for information about the DROP SYNONYM statement

5 Developing Stored Subprograms and Packages

This chapter contains:

- About Stored Subprograms

- About Packages

- About PL/SQL Identifiers

- About PL/SQL Data Types

- Creating and Managing Standalone Subprograms

- Creating and Managing Packages

- Declaring and Assigning Values to Variables and Constants

- Controlling Program Flow

- Using Records and Cursors

- Using Associative Arrays

- Handling Exceptions (Runtime Errors)

About Stored Subprograms

A subprogram is a PL/SQL unit that consists of SQL and PL/SQL statements that solve a specific problem or perform a set of related tasks. A subprogram can have parameters, whose values are supplied by the invoker. A subprogram can be either a procedure or a function. Typically, you use a procedure to perform an action and a function to compute and return a value.

A stored subprogram is a subprogram that is stored in the database. Because they are stored in the database, stored programs can be used as building blocks for many different database applications. (A subprogram that is declared within another subprogram, or within an anonymous block, is called a nested subprogram or local subprogram. It cannot be invoked from outside the subprogram or block in which it is declared. An anonymous block is a block that is not stored in the database.)

There are two kinds of stored subprograms:

- Standalone subprogram, which is created at schema level

- Package subprogram, which is created inside a package

Standalone subprograms are useful for testing pieces of program logic, but when you are sure that they work as intended, Oracle recommends that you put them into packages.

See Also:

- Oracle Database Concepts for general information about stored subprograms

- Oracle Database PL/SQL Language Reference for complete information about PL/SQL subprograms

About Packages

A package is a PL/SQL unit that consists of related subprograms and the declared cursors and variables that they use.

Oracle recommends that you put your subprograms into packages. Some reasons are:

- Packages allow you to hide implementation details from client programs.
Hiding implementation details from client programs is a widely accepted best practice. Many Oracle customers follow this practice strictly, allowing client programs to access the database only by invoking PL/SQL subprograms. Some customers allow client programs to use SELECT statements to retrieve information from database tables, but require them to invoke PL/SQL subprograms for all business functions that change the database.

- Package subprograms must be qualified with package names when invoked from outside the package, which ensures that their names will always work when invoked from outside the package.
For example, suppose that you developed a schema-level procedure named CONTINUE before Oracle Database 11g . Oracle Database 11g introduced the CONTINUE statement. Therefore, if you ported your code to Oracle Database 11g , it would no longer compile. However, if you had developed your procedure inside a package, your code would refer to the procedure as package_name.CONTINUE, so the code would still compile.

Note:
Oracle Database Express Edition supplies many PL/SQL packages to extend database functionality and provide PL/SQL access to SQL features. You can use the supplied packages when creating your applications or for ideas in creating your own stored procedures. For information about these packages, see Oracle Database PL/SQL Packages and Types Reference.

See Also:

- Oracle Database Concepts for general information about packages

- Oracle Database PL/SQL Language Reference for more reasons to use packages

- Oracle Database PL/SQL Language Reference for complete information about PL/SQL packages

- Oracle Database PL/SQL Packages and Types Reference for complete information about the PL/SQL packages that Oracle provides

About PL/SQL Identifiers

Every PL/SQL subprogram, package, parameter, variable, constant, exception, and declared cursor has a name, which is a PL/SQL identifier.

The minimum length of an identifier is one character; the maximum length is 30 characters. The first character must be a letter, but each later character can be either a letter, numeral, dollar sign ($), underscore (_), or number sign (#). For example, these are acceptable identifiers:

X
t2
phone#
credit_limit
LastName
oracle$number
money$$$tree
SN##
try_again_

PL/SQL is not case-sensitive for identifiers. For example, PL/SQL considers these to be the same:

lastname
LastName
LASTNAME

You cannot use a PL/SQL reserved word as an identifier. You can use a PL/SQL keyword as an identifier, but it is not recommended. For lists of PL/SQL reserved words and keywords, see Oracle Database PL/SQL Language Reference.

See Also:

- Oracle Database PL/SQL Language Reference for additional general information about PL/SQL identifiers

- Oracle Database PL/SQL Language Reference for additional information about PL/SQL naming conventions

- Oracle Database PL/SQL Language Reference for information about the scope and visibility of PL/SQL identifiers

- Oracle Database PL/SQL Language Reference for information how to collect data on PL/SQL identifiers

- Oracle Database PL/SQL Language Reference for information about how PL/SQL resolves identifier names

About PL/SQL Data Types

Every PL/SQL constant, variable, subprogram parameter, and function return value has a data type that determines its storage format, constraints, valid range of values, and operations that can be performed on it.

A PL/SQL data type is either a SQL data type (such as VARCHAR2, NUMBER, or DATE) or a PL/SQL-only data type. The latter include BOOLEAN, RECORD, REF CURSOR, and many predefined subtypes. PL/SQL also lets you define your own subtypes.

A subtype is a subset of another data type, which is called its base type. A subtype has the same valid operations as its base type, but only a subset of its valid values. Subtypes can increase reliability, provide compatibility with ANSI/ISO types, and improve readability by indicating the intended use of constants and variables.

The predefined numeric subtype PLS_INTEGER is especially useful, because its operations use hardware arithmetic, rather than the library arithmetic that its base type uses.

You cannot use PL/SQL-only data types at schema level (that is, in tables or standalone subprograms). Therefore, to use these data types in a stored subprogram, you must put them in a package.

See Also:

- Oracle Database PL/SQL Language Reference for general information about PL/SQL data types

- Oracle Database PL/SQL Language Reference for information about the PLS_INTEGER data type

- "About SQL Data Types"

Creating and Managing Standalone Subprograms

This section contains:

- About Subprogram Structure

- Tutorial: Creating a Standalone Procedure

- Tutorial: Creating a Standalone Function

- Changing Standalone Subprograms

- Tutorial: Testing a Standalone Function

- Dropping Standalone Subprograms

Note:
To do the tutorials in this document, you must be connected to Oracle Database Express Edition as the user HR from SQL Developer.

About Subprogram Structure

A subprogram follows PL/SQL block structure; that is, it has:

- Declarative part (optional)
The declarative part contains declarations of types, constants, variables, exceptions, declared cursors, and nested subprograms. These items are local to the subprogram and cease to exist when the subprogram completes execution.

- Executable part (required)
The executable part contains statements that assign values, control execution, and manipulate data.

- Exception-handling part (optional)
The exception-handling part contains code that handles exceptions (runtime errors).

Comments can appear anywhere in PL/SQL code. The PL/SQL compiler ignores them. Adding comments to your program promotes readability and aids understanding. A single-line comment starts with a double hyphen (--) and extends to the end of the line. A multiline comment starts with a slash and asterisk (/*) and ends with an asterisk and a slash (*/).

The structure of a procedure is:

PROCEDURE name [ ( parameter_list ) ]
{ IS | AS }
[ declarative_part ]
BEGIN  -- executable part begins
statement; [ statement; ]...
[ EXCEPTION -- executable part ends, exception-handling part begins]
exception_handler; [ exception_handler; ]... ]
END; /* exception-handling part ends if it exists;
otherwise, executable part ends */

The structure of a function is like that of a procedure, except that it includes a RETURN clause and at least one RETURN statement (and some optional clauses that are beyond the scope of this document):

FUNCTION name [ ( parameter_list ) ] RETURN data_type [ clauses ]
{ IS | AS }
[ declarative_part ]
BEGIN  -- executable part begins
-- at least one statement must be a RETURN statement
statement; [ statement; ]...
[ EXCEPTION -- executable part ends, exception-handling part begins]
exception_handler; [ exception_handler; ]... ]
END; /* exception-handling part ends if it exists;
otherwise, executable part ends */

The code that begins with PROCEDURE or FUNCTION and ends before IS or AS is the subprogram signature. The declarative, executable, and exception-handling parts comprise the subprogram body. The syntax of exception-handler is in "About Exceptions and Exception Handlers".

See Also:
Oracle Database PL/SQL Language Reference for more information about subprogram parts

Tutorial: Creating a Standalone Procedure

To create a standalone procedure, use either the SQL Developer tool Create Procedure or the DDL statement CREATE PROCEDURE.

This tutorial shows how to use the Create Procedure tool to create a standalone procedure named ADD_EVALUATION that adds a row to the EVALUATIONS table created in Example 4-1.

To create a standalone procedure using Create Procedure tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, right-click Procedures.

3. In the list of choices, click New Procedure.
The Create Procedure window opens.

4. For Schema, accept the default value, HR.

5. For Name, change PROCEDURE1 to ADD_EVALUATION.

6. Click the icon Add Parameter.

A row appears under the column headings. Its fields have these default values: Name, PARAM1; Mode, IN; No Copy, deselected; Data Type, VARCHAR2; Default Value, empty.

7. For Name, change PARAM1 to EVALUATION_ID.

8. For Mode, accept the default value, IN.

9. For Data Type, select NUMBER from the menu.

10. Leave Default Value empty.

11. Add a second parameter by repeating steps 6 through 10 with the Name EMPLOYEE_ID and the Data Type NUMBER.

12. Add a third parameter by repeating steps 6 through 10 with the Name EVALUATION_DATE and the Data Type DATE.

13. Add a fourth parameter by repeating steps 6 through 10 with the Name JOB_ID and the Data Type VARCHAR2.

14. Add a fifth parameter by repeating steps 6 through 10 with the Name MANAGER_ID and the Data Type NUMBER.

15. Add a sixth parameter by repeating steps 6 through 10 with the Name DEPARTMENT_ID and the Data Type NUMBER.

16. Add a seventh parameter by repeating steps 6 through 10 with the Name TOTAL_SCORE and the Data Type NUMBER.

17. Click OK.
The ADD_EVALUATION pane opens, showing the CREATE PROCEDURE statement that created the procedure:

CREATE OR REPLACE PROCEDURE ADD_EVALUATION
(
EVALUATION_ID IN NUMBER
, EMPLOYEE_ID IN NUMBER
, EVALUATION_DATE IN DATE
, JOB_ID IN VARCHAR2
, MANAGER_ID IN NUMBER
, DEPARTMENT_ID IN NUMBER
, TOTAL_SCORE IN NUMBER
) AS
BEGIN
NULL;
END ADD_EVALUATION;

The title of the ADD_EVALUATION pane is in italic font, indicating that the procedure is not yet saved in the database.

Because the only statement in the execution part of the procedure is NULL, the procedure does nothing.

18. Replace NULL with this statement:

INSERT INTO EVALUATIONS (
evaluation_id,
employee_id,
evaluation_date,
job_id,
manager_id,
department_id,
total_score
)
VALUES (
ADD_EVALUATION.evaluation_id,
ADD_EVALUATION.employee_id,
ADD_EVALUATION.evaluation_date,
ADD_EVALUATION.job_id,
ADD_EVALUATION.manager_id,
ADD_EVALUATION.department_id,
ADD_EVALUATION.total_score
);

(Qualifying the parameter names with the procedure name ensures that they are not confused with the columns that have the same names.)

19. From the File menu, select Save.
Oracle Database Express Edition compiles the procedure and saves it. The title of the ADD_EVALUATION pane is no longer in italic font. The Message - Log has the message "Compiled".

See Also:

- Oracle SQL Developer User's Guide for another example of using SQL Developer to create a standalone procedure

- "About Data Definition Language (DDL) Statements" for general information that applies to the CREATE PROCEDURE statement

- Oracle Database PL/SQL Language Reference for information about the CREATE PROCEDURE statement

Tutorial: Creating a Standalone Function

To create a standalone function, use either the SQL Developer tool Create Function or the DDL statement CREATE FUNCTION.

This tutorial shows how to use the Create Function tool to create a standalone function named CALCULATE_SCORE that has three parameters and returns a value of type NUMBER.

To create a standalone function using Create Function tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, right-click Functions.

3. In the list of choices, click New Function.
The Create Function window opens.

4. For Schema, accept the default value, HR.

5. For Name, change FUNCTION1 to CALCULATE_SCORE.

6. For Return Type, select NUMBER from the menu.

7. Click the icon Add Parameter.

A row appears under the column headings. Its fields have these default values: Name, PARAM1; Mode, IN; No Copy, deselected; Data Type, VARCHAR2; Default Value, empty.

8. For Name, change PARAM1 to cat.

9. For Mode, accept the default value, IN.

10. For Data Type, accept the default, VARCHAR2.

11. Leave Default Value empty.

12. Add a second parameter by repeating steps 7 through 11 with the Name score and the Type NUMBER.

13. Add a third parameter by repeating steps 7 through 11 with the Name weight and the Type NUMBER.

14. Click OK.
The CALCULATE_SCORE pane opens, showing the CREATE FUNCTION statement that created the function:

CREATE OR REPLACE FUNCTION CALCULATE_SCORE
(
CAT IN VARCHAR2
, SCORE IN NUMBER
, WEIGHT IN NUMBER
) RETURN NUMBER AS
BEGIN
RETURN NULL;
END CALCULATE_SCORE;

The title of the CALCULATE_SCORE pane is in italic font, indicating that the function is not yet saved in the database.

Because the only statement in the execution part of the function is RETURN NULL, the function does nothing.

15. Replace NULL with score * weight.

16. From the File menu, select Save.
Oracle Database Express Edition compiles the function and saves it. The title of the CALCULATE_SCORE pane is no longer in italic font. The Message - Log has the message "Compiled".

See Also:

- "About Data Definition Language (DDL) Statements" for general information that applies to the CREATE FUNCTION statement

- Oracle Database PL/SQL Language Reference for information about the CREATE FUNCTION statement

Changing Standalone Subprograms

To change a standalone subprogram, use either the SQL Developer tool Edit or the DDL statement ALTER PROCEDURE or ALTER FUNCTION.

To change a standalone subprogram using the Edit tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand either Functions or Procedures.
A list of functions or procedures appears.

3. Click the function or procedure to change.
To the right of the Connections frame, a frame appears. Its top tab has the name of the subprogram to change. The Code pane shows the code that created the subprogram.

The Code pane is in write mode. (Clicking the pencil icon switches the mode from write mode to read only, or the reverse.)

4. In the Code pane, change the code.
The title of the pane changes to italic font, indicating that the change is not yet saved in the database.

5. From the File menu, select Save.
Oracle Database Express Edition compiles the subprogram and saves it. The title of the pane is no longer in italic font. The Message - Log has the message "Compiled".

See Also:

- "About Data Definition Language (DDL) Statements" for general information that applies to the ALTER PROCEDURE and ALTER FUNCTION statements

- Oracle Database PL/SQL Language Reference for information about the ALTER PROCEDURE statement

- Oracle Database PL/SQL Language Reference for information about the ALTER FUNCTION statement

Tutorial: Testing a Standalone Function

This tutorial shows how to use the SQL Developer tool Run to test the standalone function CALCULATE_SCORE.

To test the CALCULATE_SCORE function using the Run tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand Functions.

3. In the list of functions, right-click CALCULATE_SCORE.

4. In the list of choices, click Run.
The Run PL/SQL window opens. Its PL/SQL Block frame includes this code:

v_Return := CALCULATE_SCORE (
CAT => CAT,
SCORE => SCORE,
WEIGHT => WEIGHT
);

5. Change the values of SCORE and WEIGHT to 8 and 0.2, respectively:

v_Return := CALCULATE_SCORE (
CAT => CAT,
SCORE => 8,
WEIGHT => 0.2
);

6. Click OK.
Under the Code pane, the Running window opens, showing this result:

Connecting to the database hr_conn.
Process exited.
Disconnecting from the database hr_conn.

To the right of the tab Running is the tab Output Variables.

7. Click the tab Output Variables.
Two frames appear, Variable and Value, which contain <Return Value> and 1.6, respectively.

See Also:
Oracle SQL Developer User's Guide for information about using SQL Developer to run and debug procedures and functions

Dropping Standalone Subprograms

To drop a standalone subprogram, use either the SQL Developer Connections frame and Drop tool, or the DDL statement DROP PROCEDURE or DROP FUNCTION.

Caution:
Do not drop the procedure ADD_EVALUATION or the function CALCULATE_SCORE—you need them for later tutorials. If you want to practice dropping subprograms, create simple ones and then drop them.

To drop a standalone subprogram using the Drop tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand either Functions or Procedures.

3. In the list of functions or procedures, right-click the name of the function or procedure to drop.

4. In the list of choices, click Drop.

5. In the Drop window, click Apply.

6. In the Confirmation window, click OK.

See Also:

- "About Data Definition Language (DDL) Statements" for general information that applies to the DROP PROCEDURE and DROP FUNCTION statements

- Oracle Database SQL Language Reference for information about the DROP PROCEDURE statement

- Oracle Database SQL Language Reference for information about the DROP FUNCTION statement

Creating and Managing Packages

This section contains:

- About Package Structure

- Tutorial: Creating a Package Specification

- Tutorial: Changing a Package Specification

- Tutorial: Creating a Package Body

- Dropping a Package

See Also:
"Tutorial: Declaring Variables and Constants in a Subprogram", which shows how to change a package body

About Package Structure

A package always has a specification, and it usually has a body.

The package specification defines the package, declaring the types, variables, constants, exceptions, declared cursors, and subprograms that can be referenced from outside the package. A package specification is an application program interface (API): It has all the information that client programs need to invoke its subprograms, but no information about their implementation.

The package body defines the queries for the declared cursors, and the code for the subprograms, that are declared in the package specification (therefore, a package with neither declared cursors nor subprograms does not need a body). The package body can also define local subprograms, which are not declared in the specification and can be invoked only by other subprograms in the package. Package body contents are hidden from client programs. You can change the package body without invalidating the applications that call the package.

See Also:

- Oracle Database PL/SQL Language Reference for more information about the package specification

- Oracle Database PL/SQL Language Reference for more information about the package body

Tutorial: Creating a Package Specification

To create a package specification, use either the SQL Developer tool Create Package or the DDL statement CREATE PACKAGE.

This tutorial shows how to use the Create Package tool to create a specification for a package named EMP_EVAL, which appears in many tutorials and examples in this document.

To create a package specification using Create Package tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, right-click Packages.

3. In the list of choices, click New Package.
The Create Package window opens. The field Schema has the value HR, the field Name has the default value PACKAGE1, and the check box Add New Source In Lowercase is deselected.

4. For Schema, accept the default value, HR.

5. For Name, change PACKAGE1 to EMP_EVAL.

6. Click OK.
The EMP_EVAL pane opens, showing the CREATE PACKAGE statement that created the package:

CREATE OR REPLACE PACKAGE emp_eval AS

/* TODO enter package declarations (types, exceptions, methods etc) here */

END emp_eval;

The title of the pane is in italic font, indicating that the package is not saved to the database.

7. (Optional) In the CREATE PACKAGE statement, replace the comment with declarations.
If you do not do this step now, you can do it later, as in "Tutorial: Changing a Package Specification".

8. From the File menu, select Save.
Oracle Database Express Edition compiles the package and saves it. The title of the EMP_EVAL pane is no longer in italic font.

See Also:
Oracle Database PL/SQL Language Reference for information about the CREATE PACKAGE statement (for the package specification)

Tutorial: Changing a Package Specification

To change a package specification, use either the SQL Developer tool Edit or the DDL statement CREATE PACKAGE with the OR REPLACE clause.

This tutorial shows how to use the Edit tool to change the specification for the EMP_EVAL package, which appears in many tutorials and examples in this document. Specifically, the tutorial shows how to add declarations for a procedure, EVAL_DEPARTMENT, and a function, CALCULATE_SCORE.

To change EMP_EVAL package specification using the Edit tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand Packages.

3. In the list of packages, right-click EMP_EVAL.

4. In the list of choices, click Edit.
The EMP_EVAL pane opens, showing the CREATE PACKAGE statement that created the package:

CREATE OR REPLACE PACKAGE emp_eval AS

/* TODO enter package declarations (types, exceptions, methods etc) here */

END emp_eval;

The title of the pane is not in italic font, indicating that the package is saved in the database.

5. In the EMP_EVAL pane, replace the comment with this code:

PROCEDURE eval_department ( dept_id IN NUMBER );

FUNCTION calculate_score ( evaluation_id IN NUMBER
, performance_id IN NUMBER)
RETURN NUMBER;

The title of the EMP_EVAL pane changes to italic font, indicating that the changes have not been saved to the database.

6. Click the icon Compile.
The changed package specification compiles and is saved to the database. The title of the EMP_EVAL pane is no longer in italic font.

See Also:
Oracle Database PL/SQL Language Reference for information about the CREATE PACKAGE statement with the OR REPLACE clause

Tutorial: Creating a Package Body

To create a package body, use either the SQL Developer tool Create Body or the DDL statement CREATE PACKAGE BODY.

This tutorial shows how to use the Create Body tool to create a body for the EMP_EVAL package, which appears in many examples and tutorials in this document.

To create a body for the package EMP_EVAL using the Create Body tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand Packages.

3. In the list of packages, right-click EMP_EVAL.

4. In the list of choices, click Create Body.
The EMP_EVAL Body pane appears, showing the automatically generated code for the package body:

CREATE OR REPLACE
PACKAGE BODY EMP_EVAL AS

PROCEDURE eval_department(dept_id IN NUMBER) AS
BEGIN
-- TODO implementation required for PROCEDURE EMP_EVAL.eval_department
NULL;
END eval_department;

FUNCTION calculate_score ( evaluation_id IN NUMBER
, performance_id IN NUMBER)
RETURN NUMBER AS
BEGIN
-- TODO implementation required for FUNCTION EMP_EVAL.calculate_score
RETURN NULL;
END calculate_score;

END EMP_EVAL;

The title of the pane is in italic font, indicating that the code is not saved in the database.

5. (Optional) In the CREATE PACKAGE BODY statement:

- Replace the comments with executable statements.

- (Optional) In the executable part of the procedure, either delete NULL or replace it with an executable statement.

- (Optional) In the executable part of the function, either replace NULL with another expression.

If you do not do this step now, you can do it later, as in "Tutorial: Declaring Variables and Constants in a Subprogram".

6. Click the icon Compile.
The changed package body compiles and is saved to the database. The title of the EMP_EVAL Body pane is no longer in italic font.

See Also:
Oracle Database PL/SQL Language Reference for information about the CREATE PACKAGE BODY statement (for the package body)

Dropping a Package

To drop a package (both specification and body), use either the SQL Developer Connections frame and Drop tool, or the DDL statement DROP PACKAGE.

Caution:
Do not drop the package EMP_EVAL—you need it for later tutorials. If you want to practice dropping packages, create simple ones and then drop them.

To drop a package using the Drop tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand Packages.
A list of packages appears.

3. In the list of packages, right-click the name of the package to drop.

4. In the list of choices, click Drop Package.

5. In the Drop window, click Apply.

6. In the Confirmation window, click OK.

See Also:
Oracle Database PL/SQL Language Reference for information about the DROP PACKAGE statement

Declaring and Assigning Values to Variables and Constants

One significant advantage that PL/SQL has over SQL is that PL/SQL lets you declare and use variables and constants.

A variable or constant declared in a package specification is available to any program that has access to the package. A variable or constant declared in a package body or subprogram is local to that package or subprogram.

A variable holds a value of a particular data type. Your program can change the value at runtime. A constant holds a value that cannot be changed.

A variable or constant can have any PL/SQL data type. When declaring a variable, you can assign it an initial value; if you do not, its initial value is NULL. When declaring a constant, you must assign it an initial value. To assign an initial value to a variable or constant, use the assignment operator (:=).

Tip:
Declare all values that do not change as constants. This practice optimizes your compiled code and makes your source code easier to maintain.

This section contains:

- Tutorial: Declaring Variables and Constants in a Subprogram

- Ensuring that Variables, Constants, and Parameters Have Correct Data Types

- Tutorial: Changing Declarations to Use the %TYPE Attribute

- Assigning Values to Variables

See Also:
Oracle Database PL/SQL Language Reference for general information about variables and constants

Tutorial: Declaring Variables and Constants in a Subprogram

This tutorial shows how to use the SQL Developer tool Edit to declare variables and constants in the EMP_EVAL.CALCULATE_SCORE function (specified in "Tutorial: Creating a Package Specification"). (This tutorial is also an example of changing a package body.)

To declare variables and constants in CALCULATE_SCORE function:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand Packages.

3. In the list of packages, expand EMP_EVAL.

4. In the list of choices, right-click EMP_EVAL Body.
A list of choices appears.

5. In the list of choices, click Edit.
The EMP_EVAL Body pane appears, showing the code for the package body:

CREATE OR REPLACE
PACKAGE BODY EMP_EVAL AS

PROCEDURE eval_department ( dept_id IN NUMBER ) AS

BEGIN
-- TODO implementation required for PROCEDURE EMP_EVAL.eval_department
NULL;
END eval_department;

FUNCTION calculate_score ( evaluation_id IN NUMBER
, performance_id IN NUMBER)
RETURN NUMBER AS
BEGIN
-- TODO implementation required for FUNCTION EMP_EVAL.calculate_score
RETURN NULL;
END calculate_score;

END EMP_EVAL;

6. Between RETURN NUMBER AS and BEGIN, add these variable and constant declarations:

n_score       NUMBER(1,0);                -- variable
n_weight      NUMBER;                     -- variable
max_score     CONSTANT NUMBER(1,0) := 9;  -- constant, initial value 9
max_weight    CONSTANT NUMBER(8,8) := 1;  -- constant, initial value 1

The title of the EMP_EVAL Body pane changes to italic font, indicating that the code is not saved in the database.

7. From the File menu, select Save.
Oracle Database Express Edition compiles and saves the changed package body. The title of the EMP_EVAL Body pane is no longer in italic font.

See Also:

- Oracle Database PL/SQL Language Reference for general information about declaring variables and constants

- "Assigning Values to Variables with the Assignment Operator"

Ensuring that Variables, Constants, and Parameters Have Correct Data Types

After "Tutorial: Declaring Variables and Constants in a Subprogram", the code for the EMP_EVAL.CALCULATE_SCORE function is:

FUNCTION calculate_score ( evaluation_id IN NUMBER
, performance_id IN NUMBER )
RETURN NUMBER AS
n_score       NUMBER(1,0);                -- variable
n_weight      NUMBER;                     -- variable
max_score     CONSTANT NUMBER(1,0) := 9;  -- constant, initial value 9
max_weight    CONSTANT NUMBER(8,8) := 1;  -- constant, initial value 1
BEGIN
-- TODO implementation required for FUNCTION EMP_EVAL.calculate_score
RETURN NULL;
END calculate_score;

The variables, constants, and parameters of the function represent values from the tables SCORES and PERFORMANCE_PARTS (created in "Creating Tables"):

- Variable n_score will hold a value from the column SCORE.SCORES and constant max_score will be compared to such values.

- Variable n_weight will hold a value from the column PERFORMANCE_PARTS.WEIGHT and constant max_weight will be compared to such values.

- Parameter evaluation_id will hold a value from the column SCORE.EVALUATION_ID.

- Parameter performance_id will hold a value from the column SCORE.PERFORMANCE_ID.

Therefore, each variable, constant, and parameter has the same data type as its corresponding column.

If the data types of the columns change, you want the data types of the variables, constants, and parameters to change to the same data types; otherwise, the CALCULATE_SCORE function is invalidated.

To ensure that the data types of the variables, constants, and parameters always match those of the columns, declare them with the %TYPE attribute. The %TYPE attribute supplies the data type of a table column or another variable, ensuring the correct data type assignment.

See Also:

- Oracle Database PL/SQL Language Reference for more information about the %TYPE attribute

- Oracle Database PL/SQL Language Reference for the syntax of the %TYPE attribute

Tutorial: Changing Declarations to Use the %TYPE Attribute

This tutorial shows how to use the SQL Developer tool Edit to change the declarations of the variables, constants, and formal parameters of the EMP_EVAL.CALCULATE_SCORE function (shown in "Tutorial: Declaring Variables and Constants in a Subprogram") to use the %TYPE attribute.

To change the declarations in CALCULATE_SCORE to use %TYPE:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand Packages.

3. In the list of packages, expand EMP_EVAL.

4. In the list of choices, right-click EMP_EVAL Body.

5. In the list of choices, click Edit.
The EMP_EVAL Body pane appears, showing the code for the package body:

CREATE OR REPLACE
PACKAGE BODY emp_eval AS

PROCEDURE eval_department ( dept_id IN NUMBER ) AS
BEGIN
-- TODO implementation required for PROCEDURE EMP_EVAL.eval_department
NULL;
END eval_department;

FUNCTION calculate_score ( evaluation_id IN NUMBER
, performance_id IN NUMBER )
RETURN NUMBER AS
n_score       NUMBER(1,0);                -- variable
n_weight      NUMBER;                     -- variable
max_score     CONSTANT NUMBER(1,0) := 9;  -- constant, initial value 9
max_weight    CONSTANT NUMBER(8,8) := 1;  -- constant, initial value 1
BEGIN
-- TODO implementation required for FUNCTION EMP_EVAL.calculate_score
RETURN NULL;
END calculate_score;

END emp_eval;

6. In the code for the function, make the changes shown in bold font:

FUNCTION calculate_score ( evaluation_id IN SCORES.EVALUATION_ID%TYPE
, performance_id IN SCORES.PERFORMANCE_ID%TYPE)
RETURN NUMBER AS
n_score       SCORES.SCORE%TYPE;
n_weight      PERFORMANCE_PARTS.WEIGHT%TYPE;
max_score     CONSTANT SCORES.SCORE%TYPE := 9;
max_weight    CONSTANT PERFORMANCE_PARTS.WEIGHT%TYPE := 1;

7. Right-click EMP_EVAL.

8. In the list of choices, click Edit.
The EMP_EVAL pane opens, showing the CREATE PACKAGE statement that created the package:

CREATE OR REPLACE PACKAGE EMP_EVAL AS

PROCEDURE eval_department(dept_id IN NUMBER);
FUNCTION calculate_score(evaluation_id IN NUMBER
, performance_id IN NUMBER)
RETURN NUMBER;

END EMP_EVAL;

9. In the code for the function, make the changes shown in bold font:

FUNCTION calculate_score(evaluation_id IN scores.evaluation_id%TYPE
, performance_id IN scores.performance_id%TYPE)

10. Right-click EMP_EVAL.

11. In the list of choices, click Compile.

12. Right-click EMP_EVAL Body.

13. In the list of choices, click Compile.

Assigning Values to Variables

You can assign a value to a variable in these ways:

- Use the assignment operator to assign it the value of an expression.

- Use the SELECT INTO or FETCH statement to assign it a value from a table.

- Pass it to a subprogram as an OUT or IN OUT parameter, and then assign the value inside the subprogram.

- Bind the variable to a value.

This section contains:

- Assigning Values to Variables with the Assignment Operator

- Assigning Values to Variables with the SELECT INTO Statement

See Also:

- Oracle Database PL/SQL Language Reference for more information about assigning values to variables

- Oracle Database Express Edition 2 Day + .NET Developer's Guide for Microsoft Windows for information about binding variables

- Oracle Database Express Edition 2 Day + PHP Developer's Guide for information about binding variables

- Oracle Database Express Edition 2 Day + Java Developer's Guide for information about binding variables

- Oracle Database Express Edition 2 Day + Application Express Developer's Guide for information about binding variables

Assigning Values to Variables with the Assignment Operator

With the assignment operator (:=), you can assign the value of an expression to a variable in either the declarative or executable part of a subprogram.

In the declarative part of a subprogram, you can assign an initial value to a variable when you declare it. The syntax is:

variable_name data_type := expression;

In the executable part of a subprogram, you can assign a value to a variable with an assignment statement. The syntax is:

variable_name := expression;

Example 5-1 shows, in bold font, the changes to make to the EMP_EVAL.CALCULATE_SCORE function to add a variable, running_total, and use it as the return value of the function. The assignment operator appears in both the declarative and executable parts of the function. (The data type of running_total must be NUMBER, rather than SCORES.SCORE%TYPE or PERFORMANCE_PARTS.WEIGHT%TYPE, because it holds the product of two NUMBER values with different precisions and scales.)

Example 5-1 Assigning Values to a Variable with Assignment Operator

FUNCTION calculate_score(evaluation_id IN SCORES.EVALUATION_ID%TYPE
, performance_id IN SCORES.PERFORMANCE_ID%TYPE)
RETURN NUMBER AS
n_score       SCORES.SCORE%TYPE;
n_weight      PERFORMANCE_PARTS.WEIGHT%TYPE;
running_total NUMBER := 0;
max_score     CONSTANT SCORES.SCORE%TYPE := 9;
max_weight    CONSTANT PERFORMANCE_PARTS.WEIGHT%TYPE:= 1;
BEGIN
running_total := max_score * max_weight;
RETURN running_total;
END calculate_score;

See Also:

- Oracle Database PL/SQL Language Reference for variable declaration syntax

- Oracle Database PL/SQL Language Reference for assignment statement syntax

Assigning Values to Variables with the SELECT INTO Statement

To use table values in subprograms or packages, you must assign them to variables with SELECT INTO statements.

Example 5-2 shows, in bold font, the changes to make to the EMP_EVAL.CALCULATE_SCORE function to have it calculate running_total from table values.

Example 5-2 Assigning Table Values to Variables with SELECT INTO

FUNCTION calculate_score ( evaluation_id IN scores.evaluation_id%TYPE
, performance_id IN scores.performance_id%TYPE )
RETURN NUMBER AS

n_score       scores.score%TYPE;
n_weight      performance_parts.weight%TYPE;
running_total NUMBER := 0;
max_score     CONSTANT scores.score%TYPE := 9;
max_weight    CONSTANT performance_parts.weight%TYPE:= 1;
BEGIN
SELECT s.score INTO n_score
FROM SCORES s
WHERE evaluation_id = s.evaluation_id
AND performance_id = s.performance_id;

SELECT p.weight INTO n_weight
FROM PERFORMANCE_PARTS p
WHERE performance_id = p.performance_id;

running_total := n_score * n_weight;
RETURN running_total;
END calculate_score;

The ADD_EVAL procedure in Example 5-3 inserts a row into the EVALUATIONS table, using values from the corresponding row in the EMPLOYEES table. Add the ADD_EVAL procedure to the body of the EMP_EVAL package, but not to the specification. Because it is not in the specification, ADD_EVAL is local to the package—it can be invoked only by other subprograms in the package, not from outside the package.

Example 5-3 Inserting a Table Row with Values from Another Table

PROCEDURE add_eval ( employee_id IN EMPLOYEES.EMPLOYEE_ID%TYPE
, today IN DATE )
AS
job_id         EMPLOYEES.JOB_ID%TYPE;
manager_id     EMPLOYEES.MANAGER_ID%TYPE;
department_id  EMPLOYEES.DEPARTMENT_ID%TYPE;
BEGIN
INSERT INTO EVALUATIONS (
evaluation_id,
employee_id,
evaluation_date,
job_id,
manager_id,
department_id,
total_score
)
SELECT
evaluations_sequence.NEXTVAL,   -- evaluation_id
add_eval.employee_id,      -- employee_id
add_eval.today,            -- evaluation_date
e.job_id,                  -- job_id
e.manager_id,              -- manager_id
e.department_id,           -- department_id
0                          -- total_score
FROM employees e;

IF SQL%ROWCOUNT = 0 THEN
RAISE NO_DATA_FOUND;
END IF;
END add_eval;

See Also:
Oracle Database PL/SQL Language Reference for more information about the SELECT INTO statement

Controlling Program Flow

Unlike SQL, which runs statements in the order in which you enter them, PL/SQL has control statements that let you control the flow of your program.

This section contains:

- About Control Statements

- Using the IF Statement

- Using the CASE Statement

- Using the FOR LOOP Statement

- Using the WHILE LOOP Statement

- Using the Basic LOOP and EXIT WHEN Statements

About Control Statements

PL/SQL has three categories of control statements:

- Conditional selection statements, which let you execute different statements for different data values.
The conditional selection statements are IF and CASE.

- Loop statements, which let you repeat the same statements with a series of different data values.
The loop statements are FOR LOOP, WHILE LOOP and basic LOOP.

The EXIT statement transfers control to the end of a loop. The CONTINUE statement exits the current iteration of a loop and transfers control to the next iteration. Both EXIT and CONTINUE have an optional WHEN clause, in which you can specify a condition.

- Sequential control statements, which let you go to a specified labeled statement or to do nothing.
The sequential control statements are GOTO and NULL.

See Also:
Oracle Database PL/SQL Language Reference for an overview of PL/SQL control statements

Using the IF Statement

The IF statement either executes or skips a sequence of statements, depending on the value of a Boolean expression.

The IF statement has this syntax:

IF boolean_expression THEN statement [, statement ]
[ ELSIF boolean_expression THEN statement [, statement ] ]...
[ ELSE  statement [, statement ] ]
END IF;

Suppose that your company evaluates employees twice a year in the first 10 years of employment, but only once a year afterward. You want a function that returns the evaluation frequency for an employee. You can use an IF statement to determine the return value of the function, as in Example 5-4.

Add the EVAL_FREQUENCY function to the body of the EMP_EVAL package, but not to the specification. Because it is not in the specification, EVAL_FREQUENCY is local to the package—it can be invoked only by other subprograms in the package, not from outside the package.

Tip:
When using a PL/SQL variable in a SQL statement, as in the second SELECT statement in Example 5-4, qualify the variable with the subprogram name to ensure that it is not mistaken for a table column.

Example 5-4 IF Statement that Determines Return Value of Function

FUNCTION eval_frequency (emp_id IN EMPLOYEES.EMPLOYEE_ID%TYPE)
RETURN PLS_INTEGER
AS
h_date     EMPLOYEES.HIRE_DATE%TYPE;
today      EMPLOYEES.HIRE_DATE%TYPE;
eval_freq  PLS_INTEGER;
BEGIN
SELECT SYSDATE INTO today FROM DUAL;

SELECT HIRE_DATE INTO h_date
FROM EMPLOYEES
WHERE EMPLOYEE_ID = eval_frequency.emp_id;

IF ((h_date + (INTERVAL '120' MONTH)) < today) THEN
eval_freq := 1;
ELSE
eval_freq := 2;
END IF;

RETURN eval_freq;
END eval_frequency;

See Also:

- Oracle Database PL/SQL Language Reference for the syntax of the IF statement

- Oracle Database PL/SQL Language Reference for more information about using the IF statement

Using the CASE Statement

The CASE statement chooses from a sequence of conditions, and executes the corresponding statement.

The simple CASE statement evaluates a single expression and compares it to several potential values. It has this syntax:

CASE expression
WHEN value THEN statement
[ WHEN value THEN statement ]...
[ ELSE statement [, statement ]... ]
END CASE;

The searched CASE statement evaluates multiple Boolean expressions and chooses the first one whose value is TRUE. For information about the searched CASE statement, see Oracle Database PL/SQL Language Reference.

Tip:
When you can use either a CASE statement or nested IF statements, use a CASE statement—it is both more readable and more efficient.

Suppose that, if an employee is evaluated only once a year, you want the EVAL_FREQUENCY function to suggest a salary increase, which depends on the JOB_ID.

Change the EVAL_FREQUENCY function as shown in bold font in Example 5-5. (For information about the procedures that prints the strings, DBMS_OUTPUT.PUT_LINE, see Oracle Database PL/SQL Packages and Types Reference.)

Example 5-5 CASE Statement that Determines Which String to Print

FUNCTION eval_frequency (emp_id IN EMPLOYEES.EMPLOYEE_ID%TYPE)
RETURN PLS_INTEGER
AS
h_date     EMPLOYEES.HIRE_DATE%TYPE;
today      EMPLOYEES.HIRE_DATE%TYPE;
eval_freq  PLS_INTEGER;
j_id       EMPLOYEES.JOB_ID%TYPE;

BEGIN
SELECT SYSDATE INTO today FROM DUAL;

SELECT HIRE_DATE, JOB_ID INTO h_date, j_id
FROM EMPLOYEES
WHERE EMPLOYEE_ID = eval_frequency.emp_id;

IF ((h_date + (INTERVAL '12' MONTH)) < today) THEN
eval_freq := 1;

CASE j_id
WHEN 'PU_CLERK' THEN DBMS_OUTPUT.PUT_LINE(
'Consider 8% salary increase for employee # ' || emp_id);
WHEN 'SH_CLERK' THEN DBMS_OUTPUT.PUT_LINE(
'Consider 7% salary increase for employee # ' || emp_id);
WHEN 'ST_CLERK' THEN DBMS_OUTPUT.PUT_LINE(
'Consider 6% salary increase for employee # ' || emp_id);
WHEN 'HR_REP' THEN DBMS_OUTPUT.PUT_LINE(
'Consider 5% salary increase for employee # ' || emp_id);
WHEN 'PR_REP' THEN DBMS_OUTPUT.PUT_LINE(
'Consider 5% salary increase for employee # ' || emp_id);
WHEN 'MK_REP' THEN DBMS_OUTPUT.PUT_LINE(
'Consider 4% salary increase for employee # ' || emp_id);
ELSE DBMS_OUTPUT.PUT_LINE(
'Nothing to do for employee #' || emp_id);
END CASE;
ELSE
eval_freq := 2;
END IF;

RETURN eval_freq;
END eval_frequency;

See Also:

- "Using CASE Expressions in Queries"

- Oracle Database PL/SQL Language Reference for the syntax of the CASE statement

- Oracle Database PL/SQL Language Reference for more information about using the CASE statement

Using the FOR LOOP Statement

The FOR LOOP statement repeats a sequence of statements once for each integer in the range lower_bound through upper_bound. Its syntax is:

FOR counter IN lower_bound..upper_bound LOOP
statement [, statement ]...
END LOOP;

The statements between LOOP and END LOOP can use counter, but cannot change its value.

Suppose that, instead of only suggesting a salary increase, you want the EVAL_FREQUENCY function to report what the salary would be if it increased by the suggested amount every year for five years.

Change the EVAL_FREQUENCY function as shown in bold font in Example 5-6. (For information about the procedure that prints the strings, DBMS_OUTPUT.PUT_LINE, see Oracle Database PL/SQL Packages and Types Reference.)

Example 5-6 FOR LOOP Statement that Computes Salary After Five Years

FUNCTION eval_frequency (emp_id IN EMPLOYEES.EMPLOYEE_ID%TYPE)
RETURN PLS_INTEGER
AS
h_date      EMPLOYEES.HIRE_DATE%TYPE;
today       EMPLOYEES.HIRE_DATE%TYPE;
eval_freq   PLS_INTEGER;
j_id        EMPLOYEES.JOB_ID%TYPE;
sal         EMPLOYEES.SALARY%TYPE;
sal_raise   NUMBER(3,3) := 0;

BEGIN
SELECT SYSDATE INTO today FROM DUAL;

SELECT HIRE_DATE, JOB_ID, SALARY INTO h_date, j_id, sal
FROM EMPLOYEES
WHERE EMPLOYEE_ID = eval_frequency.emp_id;

IF ((h_date + (INTERVAL '12' MONTH)) < today) THEN
eval_freq := 1;

CASE j_id
WHEN 'PU_CLERK' THEN sal_raise := 0.08;
WHEN 'SH_CLERK' THEN sal_raise := 0.07;
WHEN 'ST_CLERK' THEN sal_raise := 0.06;
WHEN 'HR_REP'   THEN sal_raise := 0.05;
WHEN 'PR_REP'   THEN sal_raise := 0.05;
WHEN 'MK_REP'   THEN sal_raise := 0.04;
ELSE NULL;
END CASE;

IF (sal_raise != 0) THEN
BEGIN
DBMS_OUTPUT.PUT_LINE('If salary ' || sal || ' increases by ' ||
ROUND((sal_raise * 100),0) ||
'% each year for 5 years, it will be:');

FOR i IN 1..5 LOOP
sal := sal * (1 + sal_raise);
DBMS_OUTPUT.PUT_LINE(ROUND(sal, 2) || ' after ' || i || ' year(s)');
END LOOP;
END;
END IF;

ELSE
eval_freq := 2;
END IF;

RETURN eval_freq;
END eval_frequency;

See Also:

- Oracle Database PL/SQL Language Reference for the syntax of the FOR LOOP statement

- Oracle Database PL/SQL Language Reference for more information about using the FOR LOOP statement

Using the WHILE LOOP Statement

The WHILE LOOP statement repeats a sequence of statements while a condition is TRUE. Its syntax is:

WHILE condition LOOP
statement [, statement ]...
END LOOP;

Note:
If the statements between LOOP and END LOOP never cause condition to become FALSE, then the WHILE LOOP statement runs indefinitely.

Suppose that the EVAL_FREQUENCY function uses the WHILE LOOP statement instead of the FOR LOOP statement and ends after the proposed salary exceeds the maximum salary for the JOB_ID.

Change the EVAL_FREQUENCY function as shown in bold font in Example 5-7. (For information about the procedures that prints the strings, DBMS_OUTPUT.PUT_LINE, see Oracle Database PL/SQL Packages and Types Reference.)

Example 5-7 WHILE LOOP Statement that Computes Salary to Maximum

FUNCTION eval_frequency (emp_id IN EMPLOYEES.EMPLOYEE_ID%TYPE)
RETURN PLS_INTEGER
AS
h_date      EMPLOYEES.HIRE_DATE%TYPE;
today       EMPLOYEES.HIRE_DATE%TYPE;
eval_freq   PLS_INTEGER;
j_id        EMPLOYEES.JOB_ID%TYPE;
sal         EMPLOYEES.SALARY%TYPE;
sal_raise   NUMBER(3,3) := 0;
sal_max     JOBS.MAX_SALARY%TYPE;

BEGIN
SELECT SYSDATE INTO today FROM DUAL;

SELECT HIRE_DATE, j.JOB_ID, SALARY, MAX_SALARY INTO h_date, j_id, sal, sal_max
FROM EMPLOYEES e, JOBS j
WHERE EMPLOYEE_ID = eval_frequency.emp_id AND JOB_ID = eval_frequency.j_id;

IF ((h_date + (INTERVAL '12' MONTH)) < today) THEN
eval_freq := 1;

CASE j_id
WHEN 'PU_CLERK' THEN sal_raise := 0.08;
WHEN 'SH_CLERK' THEN sal_raise := 0.07;
WHEN 'ST_CLERK' THEN sal_raise := 0.06;
WHEN 'HR_REP'   THEN sal_raise := 0.05;
WHEN 'PR_REP'   THEN sal_raise := 0.05;
WHEN 'MK_REP'   THEN sal_raise := 0.04;
ELSE NULL;
END CASE;

IF (sal_raise != 0) THEN
BEGIN
DBMS_OUTPUT.PUT_LINE('If salary ' || sal || ' increases by ' ||
ROUND((sal_raise * 100),0) ||
'% each year, it will be:');

WHILE sal <= sal_max LOOP
sal := sal * (1 + sal_raise);
DBMS_OUTPUT.PUT_LINE(ROUND(sal, 2));
END LOOP;

DBMS_OUTPUT.PUT_LINE('Maximum salary for this job is ' || sal_max);
END;
END IF;
ELSE
eval_freq := 2;
END IF;

RETURN eval_freq;
END eval_frequency;

See Also:

- Oracle Database PL/SQL Language Reference for the syntax of the WHILE LOOP statement

- Oracle Database PL/SQL Language Reference for more information about using the WHILE LOOP statement

Using the Basic LOOP and EXIT WHEN Statements

The basic LOOP statement repeats a sequence of statements. Its syntax is:

LOOP
statement [, statement ]...
END LOOP;

At least one statement must be an EXIT statement; otherwise, the LOOP statement runs indefinitely.

The EXIT WHEN statement (the EXIT statement with its optional WHEN clause) exits a loop when a condition is TRUE and transfers control to the end of the loop.

In the EVAL_FREQUENCY function, in the last iteration of the WHILE LOOP statement, the last computed value usually exceeds the maximum salary.

Change the WHILE LOOP statement to a basic LOOP statement that includes an EXIT WHEN statement, as in Example 5-8.

Example 5-8 Using the EXIT WHEN Statement

FUNCTION eval_frequency (emp_id IN EMPLOYEES.EMPLOYEE_ID%TYPE)
RETURN PLS_INTEGER
AS
h_date      EMPLOYEES.HIRE_DATE%TYPE;
today       EMPLOYEES.HIRE_DATE%TYPE;
eval_freq   PLS_INTEGER;
j_id        EMPLOYEES.JOB_ID%TYPE;
sal         EMPLOYEES.SALARY%TYPE;
sal_raise   NUMBER(3,3) := 0;
sal_max     JOBS.MAX_SALARY%TYPE;

BEGIN
SELECT SYSDATE INTO today FROM DUAL;

SELECT HIRE_DATE, j.JOB_ID, SALARY, MAX_SALARY INTO h_date, j_id, sal, sal_max
FROM EMPLOYEES e, JOBS j
WHERE EMPLOYEE_ID = eval_frequency.emp_id AND JOB_ID = eval_frequency.j_id;

IF ((h_date + (INTERVAL '12' MONTH)) < today) THEN
eval_freq := 1;

CASE j_id
WHEN 'PU_CLERK' THEN sal_raise := 0.08;
WHEN 'SH_CLERK' THEN sal_raise := 0.07;
WHEN 'ST_CLERK' THEN sal_raise := 0.06;
WHEN 'HR_REP'   THEN sal_raise := 0.05;
WHEN 'PR_REP'   THEN sal_raise := 0.05;
WHEN 'MK_REP'   THEN sal_raise := 0.04;
ELSE NULL;
END CASE;

IF (sal_raise != 0) THEN
BEGIN
DBMS_OUTPUT.PUT_LINE('If salary ' || sal || ' increases by ' ||
ROUND((sal_raise * 100),0) ||
'% each year, it will be:');

LOOP
sal := sal * (1 + sal_raise);
EXIT WHEN sal > sal_max;
DBMS_OUTPUT.PUT_LINE(ROUND(sal,2));
END LOOP;

DBMS_OUTPUT.PUT_LINE('Maximum salary for this job is ' || sal_max);
END;
END IF;
ELSE
eval_freq := 2;
END IF;

RETURN eval_freq;
END eval_frequency;

See Also:

- Oracle Database PL/SQL Language Reference for the syntax of the LOOP statement

- Oracle Database PL/SQL Language Reference for the syntax of the EXIT statement

- Oracle Database PL/SQL Language Reference for more information about using the LOOP and EXIT statements

Using Records and Cursors

This section contains:

- About Records

- Tutorial: Declaring a RECORD Type

- Tutorial: Creating and Invoking a Subprogram with a Record Parameter

- About Cursors

- Using a Declared Cursor to Retrieve Result Set Rows One at a Time

- Tutorial: Using a Declared Cursor to Retrieve Result Set Rows One at a Time

- About Cursor Variables

- Using a Cursor Variable to Retrieve Result Set Rows One at a Time

- Tutorial: Using a Cursor Variable to Retrieve Result Set Rows One at a Time

See Also:
Oracle Database PL/SQL Language Reference for more information about records

About Records

A record is a PL/SQL composite variable that can store data values of different types, similar to a struct type in C, C++, or Java. The internal components of a record are called fields. To access a record field, you use dot notation: record_name.field_name.

You can treat record fields like scalar variables. You can also pass entire records as subprogram parameters.

Records are useful for holding data from table rows, or from certain columns of table rows. Each record field corresponds to a table column.

There are three ways to create a record:

- Declare a RECORD type and then declare a variable of that type.
The syntax is:

TYPE record_name IS RECORD
( field_name data_type [:= initial_value]
[, field_name data_type [:= initial_value ] ]... );

variable_name record_name;

- Declare a variable of the type table_name%ROWTYPE.
The fields of the record have the same names and data types as the columns of the table.

- Declare a variable of the type cursor_name%ROWTYPE.
The fields of the record have the same names and data types as the columns of the table in the FROM clause of the cursor SELECT statement.

See Also:

- Oracle Database PL/SQL Language Reference for more information about defining RECORD types and declaring records of that type

- Oracle Database PL/SQL Language Reference for the syntax of a RECORD type definition

- Oracle Database PL/SQL Language Reference for more information about the %ROWTYPE attribute

- Oracle Database PL/SQL Language Reference for the syntax of the %ROWTYPE attribute

Tutorial: Declaring a RECORD Type

This tutorial shows how to use the SQL Developer tool Edit to declare a RECORD type, sal_info, whose fields can hold salary information for an employee—job ID, minimum and maximum salary for that job ID, current salary, and suggested raise.

To declare RECORD type sal_info:

1. In the Connections frame, expand hr_conn.
Under the hr_conn icon, a list of schema object types appears.

2. Expand Packages.
A list of packages appears.

3. Right-click EMP_EVAL.
A list of choices appears.

4. Click Edit.
The EMP_EVAL pane opens, showing the CREATE PACKAGE statement that created the package:

CREATE OR REPLACE PACKAGE EMP_EVAL AS

PROCEDURE eval_department(dept_id IN NUMBER);
FUNCTION calculate_score(evaluation_id IN NUMBER
, performance_id IN NUMBER)
RETURN NUMBER;

END EMP_EVAL;

5. In the EMP_EVAL pane, immediately before END EMP_EVAL, add this code:

TYPE sal_info IS RECORD
( j_id     jobs.job_id%type
, sal_min  jobs.min_salary%type
, sal_max  jobs.max_salary%type
, sal      employees.salary%type
, sal_raise NUMBER(3,3) );

The title of the pane is in italic font, indicating that the changes have not been saved to the database.

6. Click the icon Compile.
The changed package specification compiles and is saved to the database. The title of the EMP_EVAL pane is no longer in italic font.

Now you can declare records of the type sal_info, as in "Tutorial: Creating and Invoking a Subprogram with a Record Parameter".

Tutorial: Creating and Invoking a Subprogram with a Record Parameter

If you declared the RECORD type sal_info in "Tutorial: Declaring a RECORD Type", this tutorial shows how to use the SQL Developer tool Edit to do the following:

- Create a procedure, SALARY_SCHEDULE, which has a parameter of type sal_info.

- Change the EVAL_FREQUENCY function so that it declares a record, emp_sal, of the type sal_info, populates its fields, and passes it to the SALARY_SCHEDULE procedure.

Because EVAL_FREQUENCY will invoke SALARY_SCHEDULE, the declaration of SALARY_SCHEDULE must precede the declaration of EVAL_FREQUENCY (otherwise the package will not compile). However, the definition of SALARY_SCHEDULE can be anywhere in the package body.

To create SALARY_SCHEDULE and change EVAL_FREQUENCY:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand Packages.

3. In the list of packages, expand EMP_EVAL.

4. In the list of choices, right-click EMP_EVAL Body.

5. In the list of choices, click Edit.
The EMP_EVAL Body pane appears, showing the code for the package body.

6. In the EMP_EVAL Body pane, immediately before END EMP_EVAL, add this definition of the SALARY_SCHEDULE procedure:

PROCEDURE salary_schedule (emp IN sal_info) AS
accumulating_sal  NUMBER;
BEGIN
DBMS_OUTPUT.PUT_LINE('If salary ' || emp.sal ||
' increases by ' || ROUND((emp.sal_raise * 100),0) ||
'% each year, it will be:');

accumulating_sal := emp.sal;

WHILE accumulating_sal <= emp.sal_max LOOP
accumulating_sal := accumulating_sal * (1 + emp.sal_raise);
DBMS_OUTPUT.PUT_LINE(ROUND(accumulating_sal,2) ||', ');
END LOOP;
END salary_schedule;

The title of the pane is in italic font, indicating that the changes have not been saved to the database.

7. In the EMP_EVAL Body pane, enter the code shown in bold font, in this position:

CREATE OR REPLACE
PACKAGE BODY EMP_EVAL AS

FUNCTION eval_frequency (emp_id EMPLOYEES.EMPLOYEE_ID%TYPE)
RETURN PLS_INTEGER;
PROCEDURE salary_schedule(emp IN sal_info);
PROCEDURE add_eval(employee_id IN employees.employee_id%type, today IN DATE);

PROCEDURE eval_department (dept_id IN NUMBER) AS

8. Edit the EVAL_FREQUENCY function, making the changes shown in bold font:

FUNCTION eval_frequency (emp_id EMPLOYEES.EMPLOYEE_ID%TYPE)
RETURN PLS_INTEGER
AS
h_date     EMPLOYEES.HIRE_DATE%TYPE;
today      EMPLOYEES.HIRE_DATE%TYPE;
eval_freq  PLS_INTEGER;
emp_sal    SAL_INFO;  -- replaces sal, sal_raise, and sal_max

BEGIN
SELECT SYSDATE INTO today FROM DUAL;

SELECT HIRE_DATE INTO h_date
FROM EMPLOYEES
WHERE EMPLOYEE_ID = eval_frequency.emp_id;

IF ((h_date + (INTERVAL '120' MONTH)) < today) THEN
eval_freq := 1;

/* populate emp_sal */

SELECT j.JOB_ID, j.MIN_SALARY, j.MAX_SALARY, e.SALARY
INTO emp_sal.j_id, emp_sal.sal_min, emp_sal.sal_max, emp_sal.sal
FROM EMPLOYEES e, JOBS j
WHERE e.EMPLOYEE_ID = eval_frequency.emp_id
AND j.JOB_ID = eval_frequency.emp_id;

emp_sal.sal_raise := 0;  -- default

CASE emp_sal.j_id
WHEN 'PU_CLERK' THEN emp_sal.sal_raise := 0.08;
WHEN 'SH_CLERK' THEN emp_sal.sal_raise := 0.07;
WHEN 'ST_CLERK' THEN emp_sal.sal_raise := 0.06;
WHEN 'HR_REP' THEN emp_sal.sal_raise := 0.05;
WHEN 'PR_REP' THEN emp_sal.sal_raise := 0.05;
WHEN 'MK_REP' THEN emp_sal.sal_raise := 0.04;
ELSE NULL;
END CASE;

IF (emp_sal.sal_raise != 0) THEN
salary_schedule(emp_sal);
END IF;
ELSE
eval_freq := 2;
END IF;

RETURN eval_freq;
END eval_frequency;

9. Click Compile.

About Cursors

When Oracle Database Express Edition executes a SQL statement, it stores the result set and processing information in an unnamed private SQL area. A pointer to this unnamed area, called a cursor, lets you retrieve the result set one row at a time. Cursor attributes return information about the state of the cursor.

Every time you run either a SQL DML statement or a PL/SQL SELECT INTO statement, PL/SQL opens an implicit cursor. You can get information about this cursor from its attributes, but you cannot control it. After the statement runs, the database closes the cursor; however, its attribute values remain available until another DML or SELECT INTO statement runs.

PL/SQL also lets you declare cursors. A declared cursor has a name and is associated with a query (SQL SELECT statement)—usually one that returns multiple rows. After declaring a cursor, you must process it, either implicitly or explicitly. To process the cursor implicitly, use a cursor FOR LOOP. The syntax is:

FOR record_name IN cursor_name LOOP
statement
[ statement ]...
END LOOP;

To process the cursor explicitly, open it (with the OPEN statement), fetch rows from the result set either one at a time or in bulk (with the FETCH statement), and close the cursor (with the CLOSE statement). After closing the cursor, you can neither fetch records from the result set nor see the cursor attribute values.

The syntax for the value of an implicit cursor attribute is SQLattribute (for example, SQL%FOUND). SQLattribute always refers to the most recently run DML or SELECT INTO statement.

The syntax for the value of a declared cursor attribute is cursor_name immediately followed by attribute (for example, c1%FOUND).

Table 5-1 lists the cursor attributes and the values that they can return. (Implicit cursors have additional attributes that are beyond the scope of this book.)

Table 5-1 Cursor Attribute Values

Attribute

Values for Declared Cursor

Values for Implicit Cursor

%FOUND

If cursor is openFoot 1  but no fetch was attempted, NULL.

If the most recent fetch returned a row, TRUE.

If the most recent fetch did not return a row, FALSE.

If no DML or SELECT INTO statement has run, NULL.

If the most recent DML or SELECT INTO statement returned a row, TRUE.

If the most recent DML or SELECT INTO statement did not return a row, FALSE.

%NOTFOUND

If cursor is openFootref 1 but no fetch was attempted, NULL.

If the most recent fetch returned a row, FALSE.

If the most recent fetch did not return a row, TRUE.

If no DML or SELECT INTO statement has run, NULL.

If the most recent DML or SELECT INTO statement returned a row, FALSE.

If the most recent DML or SELECT INTO statement did not return a row, TRUE.

%ROWCOUNT

If cursor is openFootref 1, a number greater than or equal to zero.

NULL if no DML or SELECT INTO statement has run; otherwise, a number greater than or equal to zero.

%ISOPEN

If cursor is open, TRUE; if not, FALSE.

Always FALSE.

Footnote 1 If the cursor is not open, the attribute raises the predefined exception INVALID_CURSOR.

See Also:

- "About Queries"

- "About Data Manipulation Language (DML) Statements"

- Oracle Database Advanced Application Developer's Guide for more information about using cursors in PL/SQL

- Oracle Database PL/SQL Language Reference for more information about the SELECT INTO statement

- Oracle Database PL/SQL Language Reference for more information about managing cursors in PL/SQL

Using a Declared Cursor to Retrieve Result Set Rows One at a Time

The following procedure uses each necessary statement in its simplest form, but provides references to its complete syntax.

To use a declared cursor to retrieve result set rows one at a time:

1. In the declarative part:

1. Declare the cursor:

CURSOR cursor_name IS query;

For complete declared cursor declaration syntax, see Oracle Database PL/SQL Language Reference.

2. Declare a record to hold the row returned by the cursor:

record_name cursor_name%ROWTYPE;

For complete %ROWTYPE syntax, see Oracle Database PL/SQL Language Reference.

2. In the executable part:

1. Open the cursor:

OPEN cursor_name;

For complete OPEN statement syntax, see Oracle Database PL/SQL Language Reference.

2. Fetch rows from the cursor (rows from the result set) one at a time, using a LOOP statement that has syntax similar to this:

LOOP
FETCH cursor_name INTO record_name;
EXIT WHEN cursor_name%NOTFOUND;
-- Process row that is in record_name:
statement;
[ statement; ]...
END LOOP;

For complete FETCH statement syntax, see Oracle Database PL/SQL Language Reference.

3. Close the cursor:

CLOSE cursor_name;

For complete CLOSE statement syntax, see Oracle Database PL/SQL Language Reference.

Tutorial: Using a Declared Cursor to Retrieve Result Set Rows One at a Time

This tutorial shows how to implement the procedure EMP_EVAL.EVAL_DEPARTMENT, which uses a declared cursor, emp_cursor.

To implement the EMP_EVAL.EVAL_DEPARTMENT procedure:

1. In the EMP_EVAL package specification, change the declaration of the EVAL_DEPARTMENT procedure as shown in bold font:

PROCEDURE eval_department(dept_id IN employees.department_id%TYPE);

2. In the EMP_EVAL package body, change the definition of the EVAL_DEPARTMENT procedure as shown in bold font:

PROCEDURE eval_department (dept_id IN employees.department_id%TYPE)
AS
CURSOR emp_cursor IS
SELECT * FROM EMPLOYEES
WHERE DEPARTMENT_ID = eval_department.dept_id;

emp_record  EMPLOYEES%ROWTYPE;  -- for row returned by cursor
all_evals   BOOLEAN;  -- true if all employees in dept need evaluations
today       DATE;

BEGIN
today := SYSDATE;

IF (EXTRACT(MONTH FROM today) < 6) THEN
all_evals := FALSE; -- only new employees need evaluations
ELSE
all_evals := TRUE;  -- all employees need evaluations
END IF;

OPEN emp_cursor;

DBMS_OUTPUT.PUT_LINE (
'Determining evaluations necessary in department # ' ||
dept_id );

LOOP
FETCH emp_cursor INTO emp_record;
EXIT WHEN emp_cursor%NOTFOUND;

IF all_evals THEN
add_eval(emp_record.employee_id, today);
ELSIF (eval_frequency(emp_record.employee_id) = 2) THEN
add_eval(emp_record.employee_id, today);
END IF;
END LOOP;

DBMS_OUTPUT.PUT_LINE('Processed ' || emp_cursor%ROWCOUNT || ' records.');

CLOSE emp_cursor;
END eval_department;

(For a step-by-step example of changing a package body, see "Tutorial: Declaring Variables and Constants in a Subprogram".)

3. Compile the EMP_EVAL package specification.

4. Compile the EMP_EVAL package body.

About Cursor Variables

A cursor variable is like a cursor (see "About Cursors"), except that it is not limited to one query. You can open a cursor variable for a query, process the result set, and then use the cursor variable for another query. Cursor variables are useful for passing query results between subprograms.

To declare a cursor variable, you declare a REF CURSOR type, and then declare a variable of that type (therefore, a cursor variable is often called a REF CURSOR). A REF CURSOR type can be either strong or weak.

A strong REF CURSOR type specifies a return type, which is the RECORD type of its cursor variables. The PL/SQL compiler does not allow you to use these strongly typed cursor variables for queries that return rows that are not of the return type. Strong REF CURSOR types are less error-prone than weak ones, but weak ones are more flexible.

A weak REF CURSOR type does not specify a return type. The PL/SQL compiler accepts weakly typed cursor variables in any queries. Weak REF CURSOR types are interchangeable; therefore, instead of creating weak REF CURSOR types, you can use the predefined type weak cursor type SYS_REFCURSOR.

After declaring a cursor variable, you must open it for a specific query (with the OPEN FOR statement), fetch rows one at a time from the result set (with the FETCH statement), and then either close the cursor (with the CLOSE statement) or open it for another specific query (with the OPEN FOR statement). Opening the cursor variable for another query closes it for the previous query. After closing a cursor variable for a specific query, you can neither fetch records from the result set of that query nor see the cursor attribute values for that query.

See Also:

- Oracle Database PL/SQL Language Reference for more information about using cursor variables

- Oracle Database PL/SQL Language Reference for the syntax of cursor variable declaration

Using a Cursor Variable to Retrieve Result Set Rows One at a Time

The following procedure uses each of the necessary statements in its simplest form, but provides references to their complete syntax.

To use a cursor variable to retrieve result set rows one at a time:

1. In the declarative part:

1. Declare the REF CURSOR type:

TYPE cursor_type IS REF CURSOR [ RETURN return_type ];

For complete REF CURSOR type declaration syntax, see Oracle Database PL/SQL Language Reference.

2. Declare a cursor variable of that type:

cursor_variable cursor_type;

For complete cursor variable declaration syntax, see Oracle Database PL/SQL Language Reference.

3. Declare a record to hold the row returned by the cursor:

record_name return_type;

For complete information about record declaration syntax, see Oracle Database PL/SQL Language Reference.

2. In the executable part:

1. Open the cursor variable for a specific query:

OPEN cursor_variable FOR query;

For complete information about OPEN FOR statement syntax, see Oracle Database PL/SQL Language Reference.

2. Fetch rows from the cursor variable (rows from the result set) one at a time, using a LOOP statement that has syntax similar to this:

LOOP
FETCH cursor_variable INTO record_name;
EXIT WHEN cursor_variable%NOTFOUND;
-- Process row that is in record_name:
statement;
[ statement; ]...
END LOOP;

For complete information about FETCH statement syntax, see Oracle Database PL/SQL Language Reference.

3. Close the cursor variable:

CLOSE cursor_variable;

Alternatively, you can open the cursor variable for another query, which closes it for the current query.

For complete information about CLOSE statement syntax, see Oracle Database PL/SQL Language Reference.

Tutorial: Using a Cursor Variable to Retrieve Result Set Rows One at a Time

This tutorial shows how to change the EMP_EVAL.EVAL_DEPARTMENT procedure so that it uses a cursor variable instead of a declared cursor, which lets it process multiple departments. The change includes adding a procedure that uses the cursor variable.

This tutorial also shows how to make EMP_EVAL.EVAL_DEPARTMENT and EMP_EVAL.ADD_EVAL more efficient: Instead of passing one field of a record to ADD_EVAL and having ADD_EVAL use three queries to extract three other fields of the same record, EVAL_DEPARTMENT passes the entire record to ADD_EVAL, and ADD_EVAL uses dot notation to access the values of the other three fields.

To change the EMP_EVAL.EVAL_DEPARTMENT procedure to use a cursor variable:

1. In the EMP_EVAL package specification, add the procedure declaration and the REF CURSOR type definition, as shown in bold font:

CREATE OR REPLACE
PACKAGE emp_eval AS

PROCEDURE eval_department (dept_id IN employees.department_id%TYPE);

PROCEDURE eval_everyone;

FUNCTION calculate_score(eval_id IN scores.evaluation_id%TYPE
, perf_id IN scores.performance_id%TYPE)
RETURN NUMBER;
TYPE SAL_INFO IS RECORD
( j_id jobs.job_id%type
, sal_min jobs.min_salary%type
, sal_max jobs.max_salary%type
, salary employees.salary%type
, sal_raise NUMBER(3,3));

TYPE emp_refcursor_type IS REF CURSOR RETURN employees%ROWTYPE;
END emp_eval;

2. In the EMP_EVAL package body, add a forward declaration for the procedure EVAL_LOOP_CONTROL and change the declaration of the procedure ADD_EVAL, as shown in bold font:

CREATE OR REPLACE
PACKAGE BODY EMP_EVAL AS

FUNCTION eval_frequency (emp_id IN EMPLOYEES.EMPLOYEE_ID%TYPE)
RETURN PLS_INTEGER;

PROCEDURE salary_schedule(emp IN sal_info);

PROCEDURE add_eval(emp_record IN EMPLOYEES%ROWTYPE, today IN DATE);

PROCEDURE eval_loop_control(emp_cursor IN emp_refcursor_type);
...

(For a step-by-step example of changing a package body, see "Tutorial: Declaring Variables and Constants in a Subprogram".)

3. Change the EVAL_DEPARTMENT procedure to retrieve three separate result sets based on the department, and to invoke the EVAL_LOOP_CONTROL procedure, as shown in bold font:

PROCEDURE eval_department(dept_id IN employees.department_id%TYPE) AS
emp_cursor    emp_refcursor_type;
current_dept  departments.department_id%TYPE;

BEGIN
current_dept := dept_id;

FOR loop_c IN 1..3 LOOP
OPEN emp_cursor FOR
SELECT *
FROM employees
WHERE current_dept = eval_department.dept_id;

DBMS_OUTPUT.PUT_LINE
('Determining necessary evaluations in department #' ||
current_dept);

eval_loop_control(emp_cursor);

DBMS_OUTPUT.PUT_LINE
('Processed ' || emp_cursor%ROWCOUNT || ' records.');

CLOSE emp_cursor;
current_dept := current_dept + 10;
END LOOP;
END eval_department;

4. Change the ADD_EVAL procedure as shown in bold font:

PROCEDURE add_eval(emp_record IN employees%ROWTYPE, today IN DATE)
AS
-- (Delete local variables)
BEGIN
INSERT INTO EVALUATIONS (
evaluation_id,
employee_id,
evaluation_date,
job_id,
manager_id,
department_id,
total_score
)
VALUES (
evaluations_sequence.NEXTVAL,   -- evaluation_id
emp_record.employee_id,    -- employee_id
today,                     -- evaluation_date
emp_record.job_id,         -- job_id
emp_record.manager_id,     -- manager_id
emp_record.department_id,  -- department_id
0                           -- total_score
);
END add_eval;

5. Before END EMP_EVAL, add the following procedure, which fetches the individual records from the result set and processes them:

PROCEDURE eval_loop_control (emp_cursor IN emp_refcursor_type) AS
emp_record      EMPLOYEES%ROWTYPE;
all_evals       BOOLEAN;
today           DATE;
BEGIN
today := SYSDATE;

IF (EXTRACT(MONTH FROM today) < 6) THEN
all_evals := FALSE;
ELSE
all_evals := TRUE;
END IF;

LOOP
FETCH emp_cursor INTO emp_record;
EXIT WHEN emp_cursor%NOTFOUND;

IF all_evals THEN
add_eval(emp_record, today);
ELSIF (eval_frequency(emp_record.employee_id) = 2) THEN
add_eval(emp_record, today);
END IF;
END LOOP;
END eval_loop_control;

6. Before END EMP_EVAL, add the following procedure, which retrieves a result set that contains all employees in the company:

PROCEDURE eval_everyone AS
emp_cursor emp_refcursor_type;
BEGIN
OPEN emp_cursor FOR SELECT * FROM employees;
DBMS_OUTPUT.PUT_LINE('Determining number of necessary evaluations.');
eval_loop_control(emp_cursor);
DBMS_OUTPUT.PUT_LINE('Processed ' || emp_cursor%ROWCOUNT || ' records.');
CLOSE emp_cursor;
END eval_everyone;

7. Compile the EMP_EVAL package specification.

8. Compile the EMP_EVAL package body.

Using Associative Arrays

An associative array is a type of collection.

This section contains:

- About Collections

- About Associative Arrays

- Declaring Associative Arrays

- Populating Associative Arrays

- Traversing Dense Associative Arrays

- Traversing Sparse Associative Arrays

See Also:
For more information about collections:

- Oracle Database Concepts

- Oracle Database PL/SQL Language Reference

About Collections

A collection is a PL/SQL composite variable that stores elements of the same type in a specified order, similar to a one-dimensional array. The internal components of a collection are called elements. Each element has a unique subscript that identifies its position in the collection. To access a collection element, you use subscript notation: collection_name(element_subscript).

You can treat collection elements like scalar variables. You can also pass entire collections as subprogram parameters (if neither the sending nor receiving subprogram is a standalone subprogram).

A collection method is a built-in PL/SQL subprogram that either returns information about a collection or operates on a collection. To invoke a collection method, you use dot notation: collection_name.method_name. For example, collection_name.COUNT returns the number of elements in the collection.

PL/SQL has three types of collections:

- Associative arrays (formerly called "PL/SQL tables" or "index-by tables")

- Nested tables

- Variable arrays (varrays)

This document explains only associative arrays.

See Also:

- Oracle Database PL/SQL Language Reference for more information about PL/SQL collection types

- Oracle Database PL/SQL Language Reference for more information about collection methods

About Associative Arrays

An associative array is an unbounded set of key-value pairs. Each key is unique, and serves as the subscript of the element that holds the corresponding value. Therefore, you can access elements without knowing their positions in the array, and without traversing the array.

The data type of the key can be either PLS_INTEGER or VARCHAR2 (length).

If the data type of the key is PLS_INTEGER and the associative array is indexed by integer and is dense (that is, has no gaps between elements), then every element between the first and last element is defined and has a value (which can be NULL).

If the key type is VARCHAR2 (length), the associative array is indexed by string (of length characters) and is sparse; that is, it might have gaps between elements.

When traversing a dense associative array, you need not beware of gaps between elements; when traversing a sparse associative array, you do.

To assign a value to an associative array element, you can use an assignment operator:

array_name(key) := value

If key is not in the array, then the assignment statement adds the key-value pair to the array. Otherwise, the statement changes the value of array_name(key) to value.

Associative arrays are useful for storing data temporarily. They do not use the disk space or network operations that tables require. However, because associative arrays are intended for temporary storage, you cannot manipulate them with DML statements.

If you declare an associative array in a package and assign values to the variable in the package body, then the associative array exists for the life of the database session. Otherwise, it exists for the life of the subprogram in which you declare it.

See Also:
Oracle Database PL/SQL Language Reference for more information about associative arrays

Declaring Associative Arrays

To declare an associative array, you declare an associative array type and then declare a variable of that type. The simplest syntax is:

TYPE array_type IS TABLE OF element_type INDEX BY key_type;

array_name  array_type;

An efficient way to declare an associative array is with a cursor, using the following procedure. The procedure uses each necessary statement in its simplest form, but provides references to its complete syntax.

To use a cursor to declare an associative array:

1. In the declarative part:

1. Declare the cursor:

CURSOR cursor_name IS query;

For complete declared cursor declaration syntax, see Oracle Database PL/SQL Language Reference.

2. Declare the associative array type:

TYPE array_type IS TABLE OF cursor_name%ROWTYPE
INDEX BY { PLS_INTEGER | VARCHAR2 length }

For complete associative array type declaration syntax, see Oracle Database PL/SQL Language Reference.

3. Declare an associative array variable of that type:

array_name  array_type;

For complete variable declaration syntax, see Oracle Database PL/SQL Language Reference.

Example 5-9 uses the preceding procedure to declare two associative arrays, employees_jobs and jobs_, and then declares a third associative array, job_titles, without using a cursor. The first two arrays are indexed by integer; the third is indexed by string.

Note:
The ORDER BY clause in the declaration of employees_jobs_cursor determines the storage order of the elements of the associative array employee_jobs.

Example 5-9 Declaring Associative Arrays

DECLARE
-- Declare cursor:

CURSOR employees_jobs_cursor IS
SELECT FIRST_NAME, LAST_NAME, JOB_ID
FROM EMPLOYEES
ORDER BY JOB_ID, LAST_NAME, FIRST_NAME;

-- Declare associative array type:

TYPE employees_jobs_type IS TABLE OF employees_jobs_cursor%ROWTYPE
INDEX BY PLS_INTEGER;

-- Declare associative array:

employees_jobs  employees_jobs_type;

-- Use same procedure to declare another associative array:

CURSOR jobs_cursor IS
SELECT JOB_ID, JOB_TITLE
FROM JOBS;

TYPE jobs_type IS TABLE OF jobs_cursor%ROWTYPE
INDEX BY PLS_INTEGER;

jobs_  jobs_type;

-- Declare associative array without using cursor:

TYPE job_titles_type IS TABLE OF JOBS.JOB_TITLE%TYPE
INDEX BY JOBS.JOB_ID%TYPE;  -- jobs.job_id%type is varchar2(10)

job_titles  job_titles_type;

BEGIN
NULL;
END;
/

See Also:

- "About Cursors"

- Oracle Database PL/SQL Language Reference for associative array declaration syntax

Populating Associative Arrays

The most efficient way to populate a dense associative array is usually with a SELECT statement with a BULK COLLECT INTO clause.

Note:
If a dense associative array is so large that a SELECT statement would a return a result set too large to fit in memory, then do not use a SELECT statement. Instead, populate the array with a cursor and the FETCH statement with the clauses BULK COLLECT INTO and LIMIT. For information about using the FETCH statement with BULK COLLECT clause, see Oracle Database PL/SQL Language Reference.

You cannot use a SELECT statement to populate a sparse associative array (such as job_titles in "Declaring Associative Arrays"). Instead, you must use an assignment statement inside a loop statement. For information about loop statements, see "Controlling Program Flow".

Example 5-10 uses SELECT statements to populate the associative arrays employees_jobs and jobs_, which are indexed by integer. Then it uses an assignment statement inside a FOR LOOP statement to populate the associative array job_titles, which is indexed by string.

Example 5-10 Populating Associative Arrays

-- Declarative part from Example 5-9 goes here.
BEGIN
-- Populate associative arrays indexed by integer:

SELECT FIRST_NAME, LAST_NAME, JOB_ID BULK COLLECT INTO employees_jobs
FROM EMPLOYEES ORDER BY JOB_ID, LAST_NAME, FIRST_NAME;

SELECT JOB_ID, JOB_TITLE BULK COLLECT INTO jobs_ FROM JOBS;

-- Populate associative array indexed by string:

FOR i IN 1..jobs_.COUNT() LOOP
job_titles(jobs_(i).job_id) := jobs_(i).job_title;
END LOOP;
END;
/

See Also:
"About Cursors"

Traversing Dense Associative Arrays

A dense associative array (indexed by integer) has no gaps between elements—every element between the first and last element is defined and has a value (which can be NULL). You can traverse a dense array with a FOR LOOP statement, as in Example 5-11.

When inserted in the executable part of Example 5-10, after the code that populates the employees_jobs array, the FOR LOOP statement in Example 5-11 prints the elements of the employees_jobs array in the order in which they were stored. Their storage order was determined by the ORDER BY clause in the declaration of employees_jobs_cursor, which was used to declare employees_jobs (see Example 5-9).

The upper bound of the FOR LOOP statement, employees_jobs. COUNT, invokes a collection method that returns the number of elements in the array. For more information about COUNT, see Oracle Database PL/SQL Language Reference.

Example 5-11 Traversing a Dense Associative Array

-- Code that populates employees_jobs must precede this code:

FOR i IN 1..employees_jobs.COUNT LOOP
DBMS_OUTPUT.PUT_LINE(
RPAD(employees_jobs(i).first_name, 23) ||
RPAD(employees_jobs(i).last_name,  28) ||     employees_jobs(i).job_id);
END LOOP;

Result:

William                Gietz                       AC_ACCOUNT
Shelley                Higgins                     AC_MGR
Jennifer               Whalen                      AD_ASST
Steven                 King                        AD_PRES
Lex                    De Haan                     AD_VP
Neena                  Kochhar                     AD_VP
John                   Chen                        FI_ACCOUNT
...
Jose Manuel            Urman                       FI_ACCOUNT
Nancy                  Greenberg                   FI_MGR
Susan                  Mavris                      HR_REP
David                  Austin                      IT_PROG
...
Valli                  Pataballa                   IT_PROG
Michael                Hartstein                   MK_MAN
Pat                    Fay                         MK_REP
Hermann                Baer                        PR_REP
Shelli                 Baida                       PU_CLERK
...
Sigal                  Tobias                      PU_CLERK
Den                    Raphaely                    PU_MAN
Gerald                 Cambrault                   SA_MAN
...
Eleni                  Zlotkey                     SA_MAN
Ellen                  Abel                        SA_REP
...
Clara                  Vishney                     SA_REP
Sarah                  Bell                        SH_CLERK
...
Peter                  Vargas                      ST_CLERK
Adam                   Fripp                       ST_MAN
...
Matthew                Weiss                       ST_MAN

Traversing Sparse Associative Arrays

A sparse associative array (indexed by string) might have gaps between elements. You can traverse it with a WHILE LOOP statement, as in Example 5-12.

To run the code in Example 5-12, which prints the elements of the job_titles array:

1. At the end of the declarative part of Example 5-9, insert this variable declaration:

i jobs.job_id%TYPE;

2. In the executable part of Example 5-10, after the code that populates the job_titles array, insert the code from Example 5-12.

Example 5-12 includes two collection method invocations, job_titles.FIRST and job_titles.NEXT(i). job_titles.FIRST returns the first element of job_titles, and job_titles.NEXT(i) returns the subscript that succeeds i. For more information about FIRST, see Oracle Database PL/SQL Language Reference. For more information about NEXT, see Oracle Database PL/SQL Language Reference.

Example 5-12 Traversing a Sparse Associative Array

/* Declare this variable in declarative part:

i jobs.job_id%TYPE;

Add this code to the executable part,
after code that populates job_titles:
*/

i := job_titles.FIRST;

WHILE i IS NOT NULL LOOP
DBMS_OUTPUT.PUT_LINE(RPAD(i, 12) || job_titles(i));
i := job_titles.NEXT(i);
END LOOP;

Result:

AC_ACCOUNT  Public Accountant
AC_MGR      Accounting Manager
AD_ASST     Administration Assistant
AD_PRES     President
AD_VP       Administration Vice President
FI_ACCOUNT  Accountant
FI_MGR      Finance Manager
HR_REP      Human Resources Representative
IT_PROG     Programmer
MK_MAN      Marketing Manager
MK_REP      Marketing Representative
PR_REP      Public Relations Representative
PU_CLERK    Purchasing Clerk
PU_MAN      Purchasing Manager
SA_MAN      Sales Manager
SA_REP      Sales Representative
SH_CLERK    Shipping Clerk
ST_CLERK    Stock Clerk
ST_MAN      Stock Manager

Handling Exceptions (Runtime Errors)

This section contains:

- About Exceptions and Exception Handlers

- When to Use Exception Handlers

- Handling Predefined Exceptions

- Declaring and Handling User-Defined Exceptions

See Also:
Oracle Database PL/SQL Language Reference for more information about handling PL/SQL errors

About Exceptions and Exception Handlers

When a runtime error occurs in PL/SQL code, an exception is raised. If the subprogram (or block) in which the exception is raised has an exception-handling part, then control transfers to it; otherwise, execution stops. ("About Subprogram Structure" shows where to put the exception-handling part.)

Runtime errors can arise from design faults, coding mistakes, hardware failures, and many other sources.

Oracle Database Express Edition has many predefined exceptions, which it raises automatically when a program violates database rules or exceeds system-dependent limits. For example, if a SELECT INTO statement returns no rows, then Oracle Database Express Edition raises the predefined exception NO_DATA_FOUND. For a summary of predefined PL/SQL exceptions, see Oracle Database PL/SQL Language Reference.

PL/SQL lets you define (declare) your own exceptions. An exception declaration has this syntax:

exception_name EXCEPTION;

Unlike a predefined exception, a user-defined exception must be raised explicitly, using either the RAISE statement or the DBMS_STANDARD.RAISE_APPLICATION_ERROR procedure. For example:

IF condition THEN RAISE exception_name;

For information about the DBMS_STANDARD.RAISE_APPLICATION_ERROR procedure, see Oracle Database PL/SQL Language Reference.

The exception-handling part of a subprogram contains one or more exception handlers. An exception handler has this syntax:

WHEN { exception_name [ OR exception_name ]... | OTHERS } THEN
statement; [ statement; ]...

A WHEN OTHERS exception handler handles unexpected runtime errors. If used, it must be last. For example:

EXCEPTION
WHEN exception_1 THEN
statement; [ statement; ]...
WHEN exception_2 OR exception_3 THEN
statement; [ statement; ]...
WHEN OTHERS THEN
statement; [ statement; ]...
RAISE;  -- Reraise the exception (very important).
END;

An alternative to the WHEN OTHERS exception handler is the EXCEPTION_INIT pragma, which associates a user-defined exception name with an Oracle Database error number.

See Also:

- Oracle Database PL/SQL Language Reference for more information about exception declaration syntax

- Oracle Database PL/SQL Language Reference for more information about exception handler syntax

- Oracle Database PL/SQL Language Reference for more information about the EXCEPTION_INIT pragma

When to Use Exception Handlers

Oracle recommends using exception handlers only in these situations:

- You expect an exception and want to handle it.
For example, you expect that eventually, a SELECT INTO statement will return no rows, causing Oracle Database Express Edition to raise the predefined exception NO_DATA_FOUND. You want your subprogram or block to handle that exception (which is not an error) and then continue, as in Example 5-13.

- You must relinquish or close a resource.
For example:

...
file := UTL_FILE.OPEN ...
BEGIN
statement statement]...  -- If this code fails for any reason,
EXCEPTION
WHEN OTHERS THEN
UTL_FILE.FCLOSE(file);     -- then you want to close the file.
RAISE;                     -- Reraise the exception (very important).
END;
UTL_FILE.FCLOSE(file);
...

- At the top level of the code, you want to log the error.
For example, a client process might issue this block:

BEGIN
proc(...);
EXCEPTION
WHEN OTHERS THEN
log_error_using_autonomous_transaction(...);
RAISE;  -- Reraise the exception (very important).
END;
/

Alternatively, the standalone subprogram that the client invokes can include the same exception-handling logic—but only at the top level.

Handling Predefined Exceptions

Example 5-13 shows, in bold font, how to change the EMP_EVAL.EVAL_DEPARTMENT procedure to handle the predefined exception NO_DATA_FOUND. Make this change and compile the changed procedure. (For an example of how to change a package body, see "Tutorial: Declaring Variables and Constants in a Subprogram".)

Example 5-13 Handling Predefined Exception NO_DATA_FOUND

PROCEDURE eval_department(dept_id IN employees.department_id%TYPE) AS
emp_cursor    emp_refcursor_type;
current_dept  departments.department_id%TYPE;

BEGIN
current_dept := dept_id;

FOR loop_c IN 1..3 LOOP
OPEN emp_cursor FOR
SELECT *
FROM employees
WHERE current_dept = eval_department.dept_id;

DBMS_OUTPUT.PUT_LINE
('Determining necessary evaluations in department #' ||
current_dept);

eval_loop_control(emp_cursor);

DBMS_OUTPUT.PUT_LINE
('Processed ' || emp_cursor%ROWCOUNT || ' records.');

CLOSE emp_cursor;
current_dept := current_dept + 10;
END LOOP;
EXCEPTION
WHEN NO_DATA_FOUND THEN
DBMS_OUTPUT.PUT_LINE ('The query did not return a result set');
END eval_department;

See Also:
Oracle Database PL/SQL Language Reference for more information about predefined exceptions

Declaring and Handling User-Defined Exceptions

Example 5-14 shows, in bold font, how to change the EMP_EVAL.CALCULATE_SCORE function to declare and handle two user-defined exceptions, wrong_weight and wrong_score. Make this change and compile the changed function. (For an example of how to change a package body, see "Tutorial: Declaring Variables and Constants in a Subprogram".)

Example 5-14 Handling User-Defined Exceptions

FUNCTION calculate_score ( evaluation_id IN scores.evaluation_id%TYPE
, performance_id IN scores.performance_id%TYPE )
RETURN NUMBER AS

weight_wrong  EXCEPTION;
score_wrong   EXCEPTION;
n_score       scores.score%TYPE;
n_weight      performance_parts.weight%TYPE;
running_total NUMBER := 0;
max_score     CONSTANT scores.score%TYPE := 9;
max_weight    CONSTANT performance_parts.weight%TYPE:= 1;
BEGIN
SELECT s.score INTO n_score
FROM SCORES s
WHERE evaluation_id = s.evaluation_id
AND performance_id = s.performance_id;

SELECT p.weight INTO n_weight
FROM PERFORMANCE_PARTS p
WHERE performance_id = p.performance_id;

BEGIN
IF (n_weight > max_weight) OR (n_weight < 0) THEN
RAISE weight_wrong;
END IF;
END;

BEGIN
IF (n_score > max_score) OR (n_score < 0) THEN
RAISE score_wrong;
END IF;
END;

running_total := n_score * n_weight;
RETURN running_total;

EXCEPTION
WHEN weight_wrong THEN
DBMS_OUTPUT.PUT_LINE(
'The weight of a score must be between 0 and ' || max_weight);
RETURN -1;
WHEN score_wrong THEN
DBMS_OUTPUT.PUT_LINE(
'The score must be between 0 and ' || max_score);
RETURN -1;
END calculate_score;

See Also:
Oracle Database PL/SQL Language Reference for more information about user-defined exceptions

6 Using Triggers

This chapter contains:

- About Triggers

- Creating Triggers

- Changing Triggers

- Disabling and Enabling Triggers

- About Trigger Compilation and Dependencies

- Dropping Triggers

About Triggers

A trigger is a PL/SQL unit that is stored in the database and (if it is in the enabled state) automatically executes ("fires") in response to a specified event.

A trigger has this structure:

TRIGGER trigger_name
triggering_event
[ trigger_restriction ]
BEGIN
triggered_action;
END;

The trigger_name must be unique for triggers in the schema. A trigger can have the same name as another kind of object in the schema (for example, a table); however, Oracle recommends using a naming convention that avoids confusion.

If the trigger is in the enabled state, the triggering_event causes the database to execute the triggered_action if the trigger_restriction is either TRUE or omitted. The triggering_event is associated with either a table, a view, a schema, or the database, and it is one of these:

- DML statement (described in "About Data Manipulation Language (DML) Statements")

- DDL statement (described in "About Data Definition Language (DDL) Statements")

- Database operation (SERVERERROR, LOGON, LOGOFF, STARTUP, or SHUTDOWN)

If the trigger is in the disabled state, the triggering_event does not cause the database to execute the triggered_action, even if the trigger_restriction is TRUE or omitted.

By default, a trigger is created in the enabled state. You can disable an enabled trigger, and enable a disabled trigger.

Unlike a subprogram, a trigger cannot be invoked directly. A trigger is invoked only by its triggering event, which can be caused by any user or application. You might be unaware that a trigger is executing unless it causes an error that is not handled properly.

A simple trigger can fire at exactly one of these timing points:

- Before the triggering event executes (statement-level BEFORE trigger)

- After the triggering event executes (statement-level AFTER trigger)

- Before each row that the event affects (row-level BEFORE trigger)

- After each row that the event affects (row-level AFTER trigger)

A compound trigger can fire at multiple timing points. For information about compound triggers, see Oracle Database PL/SQL Language Reference.

An INSTEAD OF trigger is defined on a view, and its triggering event is a DML statement. Instead of executing the DML statement, Oracle Database executes the INSTEAD OF trigger. For more information, see "Creating an INSTEAD OF Trigger".

A system trigger is defined on a schema or the database. A trigger defined on a schema fires for each event associated with the owner of the schema (the current user). A trigger defined on a database fires for each event associated with all users.

One use of triggers is to enforce business rules that apply to all client applications. For example, suppose that data added to the EMPLOYEES table must have a certain format, and that many client applications can add data to this table. A trigger on the table can ensure the proper format of all data added to it. Because the trigger executes whenever any client adds data to the table, no client can circumvent the rules, and the code that enforces the rules can be stored and maintained only in the trigger, rather than in every client application. For other uses of triggers, see Oracle Database PL/SQL Language Reference.

See Also:
Oracle Database PL/SQL Language Reference for complete information about triggers

Creating Triggers

To create triggers, use either the SQL Developer tool Create Trigger or the DDL statement CREATE TRIGGER. This section shows how to use both of these ways to create triggers.

By default, a trigger is created in the enabled state. To create a trigger in disabled state, use the CREATE TRIGGER statement with the DISABLE clause.

Note:
To create triggers, you must have appropriate privileges; however, for this discussion, you do not need this additional information.

This section contains:

- About OLD and NEW Pseudorecords

- Tutorial: Creating a Trigger that Logs Table Changes

- Tutorial: Creating a Trigger that Generates a Primary Key for a Row Before It Is Inserted

- Creating an INSTEAD OF Trigger

- Tutorial: Creating Triggers that Log LOGON and LOGOFF Events

Note:
To do the tutorials in this document, you must be connected to Oracle Database Express Edition as the user HR from SQL Developer.

See Also:

- Oracle SQL Developer User's Guide for information about SQL Developer dialog boxes for creating objects

- Oracle Database PL/SQL Language Reference for more information about the CREATE TRIGGER statement

- "Editing Installation Scripts that Create Triggers"

About OLD and NEW Pseudorecords

When a row-level trigger fires, the PL/SQL runtime system creates and populates the two pseudorecords OLD and NEW. They are called pseudorecords because they have some, but not all, of the properties of records.

For the row that the trigger is processing:

- For an INSERT trigger, OLD contains no values, and NEW contains the new values.

- For an UPDATE trigger, OLD contains the old values, and NEW contains the new values.

- For a DELETE trigger, OLD contains the old values, and NEW contains no values.

To reference a pseudorecord, put a colon before its name—:OLD or :NEW—as in Example 6-1.

See Also:
Oracle Database PL/SQL Language Reference for more information about OLD and NEW pseudorecords

Tutorial: Creating a Trigger that Logs Table Changes

This tutorial shows how to use the CREATE TRIGGER statement to create a trigger, EVAL_CHANGE_TRIGGER, which adds a row to the table EVALUATIONS_LOG whenever an INSERT, UPDATE, or DELETE statement changes the EVALUATIONS table.

The trigger adds the row after the triggering statement executes, and uses the conditional predicates INSERTING, UPDATING, and DELETING to determine which of the three possible DML statements fired the trigger.

EVAL_CHANGE_TRIGGER is a statement-level trigger and an AFTER trigger.

To create EVALUATIONS_LOG and EVAL_CHANGE_TRIGGER:

1. Create the EVALUATIONS_LOG table:

CREATE TABLE EVALUATIONS_LOG ( log_date DATE
, action VARCHAR2(50));

2. Create EVAL_CHANGE_TRIGGER:

CREATE OR REPLACE TRIGGER EVAL_CHANGE_TRIGGER
AFTER INSERT OR UPDATE OR DELETE
ON EVALUATIONS
DECLARE
log_action  EVALUATIONS_LOG.action%TYPE;
BEGIN
IF INSERTING THEN
log_action := 'Insert';
ELSIF UPDATING THEN
log_action := 'Update';
ELSIF DELETING THEN
log_action := 'Delete';
ELSE
DBMS_OUTPUT.PUT_LINE('This code is not reachable.');
END IF;

INSERT INTO EVALUATIONS_LOG (log_date, action)
VALUES (SYSDATE, log_action);
END;

See Also:
Oracle Database PL/SQL Language Reference for more information about conditional predicates

Tutorial: Creating a Trigger that Generates a Primary Key for a Row Before It Is Inserted

The sequence EVALUATIONS_SEQUENCE (created in "Tutorial: Creating a Sequence") generates primary keys for the EVALUATIONS table (created in "Creating Tables"). However, these primary keys are not inserted into the table automatically.

This tutorial shows how to use the SQL Developer Create Trigger tool to create a trigger named NEW_EVALUATION_TRIGGER, which fires before a row is inserted into the EVALUATIONS table, and generates the unique number for the primary key of that row, using EVALUATIONS_SEQUENCE. The trigger fires once for each row affected by the triggering INSERT statement.

NEW_EVALUATION_TRIGGER is a row-level trigger and a BEFORE trigger.

To create the NEW_EVALUATION trigger:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, right-click Triggers.

3. In the list of choices, click New Trigger.

4. In the Create Trigger window:

1. In the Name field, type NEW_EVALUATION_TRIGGER over the default value TRIGGER1.

2. For Base Object, select EVALUATIONS from the menu.

3. Move INSERT from Available Events to Selected Events.
(Select INSERT and click >.)

4. Deselect the option Statement Level.

5. Click OK.
The NEW_EVALUATION_TRIGGER pane opens, showing the CREATE TRIGGER statement that created the trigger:

CREATE OR REPLACE
TRIGGER NEW_EVALUATION_TRIGGER
BEFORE INSERT ON EVALUATIONS
FOR EACH ROW
BEGIN
NULL;
END;

The title of the NEW_EVALUATION_TRIGGER pane is in italic font, indicating that the trigger is not yet saved in the database.

5. In the CREATE TRIGGER statement, replace NULL with this:

:NEW.evaluation_id := evaluations_sequence.NEXTVAL

6. From the File menu, select Save.
Oracle Database Express Edition compiles the procedure and saves it. The title of the NEW_EVALUATION_TRIGGER pane is no longer in italic font.

Creating an INSTEAD OF Trigger

A view presents the output of a query as a table. If you want to change a view as you would change a table, then you must create INSTEAD OF triggers. Instead of changing the view, they change the underlying tables.

For example, consider the view EMP_LOCATIONS, whose NAME column is created from the LAST_NAME and FIRST_NAME columns of the EMPLOYEES table:

CREATE VIEW EMP_LOCATIONS AS
SELECT e.EMPLOYEE_ID,
e.LAST_NAME || ', ' || e.FIRST_NAME NAME,
d.DEPARTMENT_NAME DEPARTMENT,
l.CITY CITY,
c.COUNTRY_NAME COUNTRY
FROM EMPLOYEES e, DEPARTMENTS d, LOCATIONS l, COUNTRIES c
WHERE e.DEPARTMENT_ID = d.DEPARTMENT_ID AND
d.LOCATION_ID = l.LOCATION_ID AND
l.COUNTRY_ID = c.COUNTRY_ID
ORDER BY LAST_NAME;

To update the view EMP_LOCATIONS.NAME (created in "Creating Views with the CREATE VIEW Statement"), you must update EMPLOYEES.LAST_NAME and EMPLOYEES.FIRST_NAME. This is what the INSTEAD OF trigger in Example 6-1 does.

NEW and OLD are pseudorecords that the PL/SQL runtime engine creates and populates whenever a row-level trigger fires. OLD and NEW store the original and new values, respectively, of the record being processed by the trigger. They are called pseudorecords because they do not have all properties of PL/SQL records.

Example 6-1 Creating an INSTEAD OF Trigger

CREATE OR REPLACE TRIGGER update_name_view_trigger
INSTEAD OF UPDATE ON emp_locations
BEGIN
UPDATE employees SET
first_name = substr( :NEW.name, instr( :new.name, ',' )+2),
last_name = substr( :NEW.name, 1, instr( :new.name, ',')-1)
WHERE employee_id = :OLD.employee_id;
END;

See Also:

- Oracle Database PL/SQL Language Reference for more information about INSTEAD OF triggers

- Oracle Database PL/SQL Language Reference for more information about OLD and NEW

Tutorial: Creating Triggers that Log LOGON and LOGOFF Events

This tutorial shows how to use the CREATE TRIGGER statement to create two triggers, HR_LOGON_TRIGGER and HR_LOGOFF_TRIGGER. After someone logs on as user HR, HR_LOGON_TRIGGER adds a row to the table HR_USERS_LOG. Before someone logs off as user HR, HR_LOGOFF_TRIGGER adds a row to the table HR_USERS_LOG.

HR_LOGON_TRIGGER and HR_LOGOFF_TRIGGER are system triggers. HR_LOGON_TRIGGER is an AFTER trigger and HR_LOGOFF_TRIGGER is a BEFORE trigger.

To create HR_USERS_LOG, HR_LOGON_TRIGGER, and HR_LOGOFF_TRIGGER:

1. Create the HR_USERS_LOG table:

CREATE TABLE hr_users_log (
user_name VARCHAR2(30),
activity VARCHAR2(20),
event_date DATE
);

2. Create hr_logon_trigger:

CREATE OR REPLACE TRIGGER hr_logon_trigger
AFTER LOGON
ON HR.SCHEMA
BEGIN
INSERT INTO hr_users_log (user_name, activity, event_date)
VALUES (USER, 'LOGON', SYSDATE);
END;

3. Create hr_logoff_trigger:

CREATE OR REPLACE TRIGGER hr_logoff_trigger
BEFORE LOGOFF
ON HR.SCHEMA
BEGIN
INSERT INTO hr_users_log (user_name, activity, event_date)
VALUES (USER, 'LOGOFF', SYSDATE);
END;

See Also:
Oracle Database PL/SQL Language Reference for more information about system triggers

Changing Triggers

To change a trigger, use either the SQL Developer tool Edit or the DDL statement CREATE TRIGGER with the OR REPLACE clause.

To change a trigger using the Edit tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand Triggers.

3. In the list of triggers, click the trigger to change.

4. In the frame to the right of the Connections frame, the Code pane appears, showing the code that created the trigger.
The Code pane is in write mode. (Clicking the pencil icon switches the mode from write mode to read only, or the reverse.)

5. In the Code pane, change the code.
The title of the pane is in italic font, indicating that the change is not yet saved in the database.

6. From the File menu, select Save.
Oracle Database Express Edition compiles the trigger and saves it. The title of the pane is no longer in italic font.

See Also:

- "About Data Definition Language (DDL) Statements" for general information that applies to the CREATE OR REPLACE TRIGGER statement

- Oracle Database PL/SQL Language Reference for more information about the CREATE OR REPLACE TRIGGER statement

Disabling and Enabling Triggers

You might need to temporarily disable triggers if they reference objects that are unavailable, or if you must upload a large amount of data without the delay that triggers cause (as in a recovery operation). After the referenced objects become available, or you have finished uploading the data, you can re-enable the triggers.

This section contains:

- Disabling or Enabling a Single Trigger

- Disabling or Enabling All Triggers on a Single Table

See Also:

- Oracle Database PL/SQL Language Reference for more information about the ALTER TRIGGER statement

- Oracle Database SQL Language Reference for more information about the ALTER TABLE statement

Disabling or Enabling a Single Trigger

To disable or enable a single trigger, use either the Disable Trigger or Enable Trigger tool or the ALTER TRIGGER statement with the DISABLE or ENABLE clause.

For example, these statements disable and enable the eval_change_trigger:

ALTER TRIGGER eval_change_trigger DISABLE;
ALTER TRIGGER eval_change_trigger ENABLE;

To use the Disable Trigger or Enable Trigger tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand Triggers.

3. In the list of triggers, right-click the desired trigger.

4. In the list of choices, select Disable or Enable.

5. In the Disable or Enable window, click Apply.

6. In the Confirmation window, click OK.

Disabling or Enabling All Triggers on a Single Table

To disable or enable all triggers on a specific table, use either the Disable All Triggers or Enable All Triggers tool or the ALTER TABLE statement with the DISABLE ALL TRIGGERS or ENABLE ALL TRIGGERS clause.

For example, these statements disable and enable all triggers on the evaluations table:

ALTER TABLE evaluations DISABLE ALL TRIGGERS;
ALTER TABLE evaluations ENABLE ALL TRIGGERS;

To use the Disable All Triggers or Enable All Triggers tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand Tables.

3. In the list of tables, right-click the desired table.

4. In the list of choices, select Triggers.

5. In the list of choices, select Disable All or Enable All.

6. In the Disable All or Enable All window, click Apply.

7. In the Confirmation window, click OK.

About Trigger Compilation and Dependencies

Running a CREATE TRIGGER statement compiles the trigger being created. If this compilation causes an error, then the CREATE TRIGGER statement fails. To see the compilation errors, use this statement:

SELECT * FROM USER_ERRORS WHERE TYPE = 'TRIGGER';

Compiled triggers depend on the schema objects on which they are defined. For example, NEW_EVALUATION_TRIGGER depends on the EVALUATIONS table:

CREATE OR REPLACE
TRIGGER NEW_EVALUATION_TRIGGER
BEFORE INSERT ON EVALUATIONS
FOR EACH ROW
BEGIN
:NEW.evaluation_id := evaluations_seq.NEXTVAL;
END;

To see the schema objects on which triggers depend, use this statement:

SELECT * FROM ALL_DEPENDENCIES WHERE TYPE = 'TRIGGER';

If an object on which a trigger depends is dropped, or changed such that there is a mismatch between the trigger and the object, then the trigger is invalidated. The next time the trigger is invoked, it is recompiled. To recompile a trigger immediately, use the ALTER TRIGGER statement with the COMPILE clause. For example:

ALTER TRIGGER NEW_EVALUATION_TRIGGER COMPILE;

See Also:
Oracle Database PL/SQL Language Reference for more information about trigger compilation and dependencies

Dropping Triggers

You must drop a trigger before dropping the objects on which it depends.

To drop a trigger, use either the SQL Developer Connections frame and Drop tool, or the DDL statement DROP TRIGGER.

This statement drops the trigger EVAL_CHANGE_TRIGGER:

DROP TRIGGER EVAL_CHANGE_TRIGGER;

To drop a trigger using the Drop tool:

1. In the Connections frame, expand hr_conn.

2. In the list of schema object types, expand Triggers.

3. In the list of triggers, right-click the name of the trigger to drop.

4. In the list of choices, click Drop Trigger.

5. In the Drop window, click Apply.

6. In the Confirmation window, click OK.

See Also:

- "About Data Definition Language (DDL) Statements" for general information that applies to the DROP TRIGGER statement

- Oracle Database PL/SQL Language Reference for information about the DROP TRIGGER statement

7 Working in a Global Environment

This chapter contains:

- About Globalization Support Features

- About Initial NLS Parameter Values

- Viewing NLS Parameter Values

- Changing NLS Parameter Values

- About Individual NLS Parameters

- Using Unicode in Globalized Applications

About Globalization Support Features

Globalization support features enable you to develop multilingual applications that can be run simultaneously from anywhere in the world. An application can render the content of the user interface, and process data, using the native language and locale preferences of the user.

Note:
In the past, Oracle called globalization support National Language Support (NLS), but NLS is actually a subset of globalization support. NLS is the ability to choose a national language and store data using a specific character set. NLS is implemented with NLS parameters.

This section contains:

- About Language Support

- About Territory Support

- About Date and Time Formats

- About Calendar Formats

- About Numeric and Monetary Formats

- About Linguistic Sorting and String Searching

- About Length Semantics

- About Unicode and SQL National Character Data Types

See Also:
Oracle Database Globalization Support Guide for more information about globalization support features

About Language Support

Oracle Database Express Edition enables you to store, process, and retrieve data in native languages. The languages that can be stored in a database are all languages written in scripts that are encoded by Oracle-supported character sets. Through the use of Unicode databases and data types, Oracle Database supports most contemporary languages.

Additional support is available for a subset of the languages. The database can, for example, display dates using translated month names, and can sort text data according to cultural conventions.

In this document, the term language support refers to the additional language-dependent functionality, and not to the ability to store text of a specific language. For example, language support includes displaying dates or sorting text according to specific locales and cultural conventions. Additionally, for some supported languages, Oracle Database provides translated server messages and a translated user interface for the database utilities.

See Also:

- "About the NLS_LANGUAGE Parameter"

- Oracle Database Globalization Support Guide for a complete list of languages that Oracle Database Express Edition supports

- Oracle Database Globalization Support Guide for a list of languages into which Oracle Database messages are translated

About Territory Support

Oracle Database Express Edition supports cultural conventions that are specific to geographical locations. The default local time format, date format, and numeric and monetary conventions depend on the local territory setting. Setting different NLS parameters enables the database session to use different cultural settings. For example, you can set the euro (EUR) as the primary currency and the Japanese yen (JPY) as the secondary currency for a given database session, even when the territory is AMERICA.

See Also:

- "About the NLS_TERRITORY Parameter"

- Oracle Database Globalization Support Guide for a complete list of territories that Oracle Database Express Edition supports

About Date and Time Formats

Different countries have different conventions for displaying the hour, day, month, and year. For example:

Country

Date Format

Example

Time Format

Example

China

yyyy-mm-dd

2005-02-28

hh24:mi:ss

13:50:23

Estonia

dd.mm.yyyy

28.02.2005

hh24:mi:ss

13:50:23

Germany

dd.mm.rr

28.02.05

hh24:mi:ss

13:50:23

UK

dd/mm/yyyy

28/02/2005

hh24:mi:ss

13:50:23

US

mm/dd/yyyy

02/28/2005

hh:mi:ssxff am

1:50:23.555 PM

See Also:

- "About the NLS_DATE_FORMAT Parameter"

- "About the NLS_DATE_LANGUAGE Parameter"

- "About NLS_TIMESTAMP_FORMAT and NLS_TIMESTAMP_TZ_FORMAT Parameters"

- Oracle Database Globalization Support Guide for information about date/time data types and time zone support

- Oracle Database SQL Language Reference for information about date and time formats

About Calendar Formats

Oracle Database Express Edition stores this calendar information for each territory:

- First day of the week

Sunday in some cultures, Monday in others. Set by the NLS_TERRITORY parameter.

- First week of the calendar year

Some countries use week numbers for scheduling, planning, and bookkeeping. In the ISO standard, this week number can differ from the week number of the calendar year. For example, 1st Jan 2005 is in ISO week number 53 of 2004. An ISO week starts on Monday and ends on Sunday. To support the ISO standard, Oracle Database Express Edition provides the IW date format element, which returns the ISO week number. The first calendar week of the year is set by the NLS_TERRITORY parameter.

- Number of days and months in a year

Oracle Database Express Edition supports six calendar systems in addition to the Gregorian calendar, which is the default. These additional calendar systems are:

- Japanese Imperial
Has the same number of months and days as the Gregorian calendar, but the year starts with the beginning of each Imperial Era.

- ROC Official
Has the same number of months and days as the Gregorian calendar, but the year starts with the founding of the Republic of China.

- Persian
The first six months have 31 days each, the next five months have 30 days each, and the last month has either 29 days or (in leap year) 30 days.

- Thai Buddha uses a Buddhist calendar.

- Arabic Hijrah has 12 months and 354 or 355 days.

- English Hijrah has 12 months and 354 or 355 days.

The calendar system is specified by the NLS_CALENDAR parameter.

- First year of era

The Islamic calendar starts from the year of the Hegira. The Japanese Imperial calendar starts from the beginning of an Emperor's reign (for example, 1998 is the tenth year of the Heisei era).

See Also:

- "About the NLS_TERRITORY Parameter"

- "About the NLS_CALENDAR Parameter"

- Oracle Database Globalization Support Guide for information about calendar formats

About Numeric and Monetary Formats

Different countries have different numeric and monetary conventions. For example:

Country

Numeric Format

Monetary Format

China

1,234,567.89

¥1,234.56

Estonia

1 234 567,89

1 234,56 kr

Germany

1.234.567,89

1.234,56€

UK

1,234,567.89

£1,234.56

US

1,234,567.89

$1,234.56

See Also:

- "About the NLS_NUMERIC_CHARACTERS Parameter"

- "About the NLS_CURRENCY Parameter"

- "About the NLS_ISO_CURRENCY Parameter"

- "About the NLS_DUAL_CURRENCY Parameter"

- Oracle Database Globalization Support Guide for information about numeric and list parameters

- Oracle Database Globalization Support Guide for information about monetary parameters

- Oracle Database SQL Language Reference for information about number format models

About Linguistic Sorting and String Searching

Different languages have different sort orders (collating sequences). Also, different countries or cultures that use the same alphabets sort words differently. For example, in Danish, Æ is after Z, and Y and Ü are considered to be variants of the same letter.

See Also:

- "About the NLS_SORT Parameter"

- "About the NLS_COMP Parameter"

- Oracle Database Globalization Support Guide for more information about linguistic sorting and string searching

About Length Semantics

In single-byte character sets, the number of bytes and the number of characters in a string are the same. In multibyte character sets, a character or code point consists of one or more bytes. Calculating the number of characters based on byte length can be difficult in a variable-width character set. Calculating column length in bytes is called byte semantics, while measuring column length in characters is called character semantics.

Character semantics is useful for specifying the storage requirements for multibyte strings of varying widths. For example, in a Unicode database (AL32UTF8), suppose that you must have a VARCHAR2 column that can store up to five Chinese characters with five English characters. Using byte semantics, this column requires 15 bytes for the Chinese characters, which are 3 bytes long, and 5 bytes for the English characters, which are 1 byte long, for a total of 20 bytes. Using character semantics, the column requires 10 characters.

See Also:

- "About the NLS_LENGTH_SEMANTICS Parameter"

- Oracle Database Globalization Support Guide for information about character sets and length semantics

About Unicode and SQL National Character Data Types

Unicode is a character encoding system that defines every character in most of the spoken languages in the world. In Unicode, every character has a unique code, regardless of the platform, program, or language.

You can store Unicode characters in an Oracle Database Express Edition in two ways:

- You can create a Unicode database that enables you to store UTF-8 encoded characters as SQL character data types (CHAR, VARCHAR2, CLOB, and LONG).

- You can declare columns and variables that have SQL national character data types.

The SQL national character data types are NCHAR, NVARCHAR2, and NCLOB. They are also called Unicode data types, because they are used only for storing Unicode data.

The national character set, which is used for all SQL national character data types, is specified when the database is created. The national character set can be either UTF8 or AL16UTF16 (default).

When you declare a column or variable of the type NCHAR or NVARCHAR2, the length that you specify is the number of characters, not the number of bytes.

See Also:

- Oracle Database Globalization Support Guide for more information about Unicode

- Oracle Database Globalization Support Guide for more information about storing Unicode characters in an Oracle Database Express Edition

- Oracle Database Globalization Support Guide for more information about SQL national character data types

About Initial NLS Parameter Values

Except in SQL Developer, the initial values of NLS parameters are set by database initialization parameters. The DBA can set the values of initialization parameters in the initialization parameter file, and they take effect the next time the database is started.

In SQL Developer, the initial values of NLS parameters are as shown in Table 7-1.

Table 7-1 Initial Values of NLS Parameters in SQL Developer

Parameter

Initial Value

NLS_CALENDAR

GREGORIAN

NLS_CHARACTERSET

AL32UTF8

NLS_COMP

BINARY

NLS_CURRENCY

$

NLS_DATE_FORMAT

DD-MON-RR

NLS_DATE_LANGUAGE

AMERICAN

NLS_DUAL_CURRENCY

$

NLS_ISO_CURRENCY

AMERICA

NLS_LANGUAGE

AMERICAN

NLS_LENGTH_SEMANTICS

BYTE

NLS_NCHAR_CHARACTERSET

AL16UTF16

NLS_NCHAR_CONV_EXCP

FALSE

NLS_NUMERIC_CHARACTERS

.,

NLS_SORT

BINARY

NLS_TERRITORY

AMERICA

NLS_TIMESTAMP_FORMAT

DD-MON-RR HH.MI.SSXFF AM

NLS_TIMESTAMP_TZ_FORMAT

DD-MON-RR HH.MI.SSXFF AM TZR

NLS_TIME_FORMAT

HH.MI.SSXFF AM

NLS_TIME_TZ_FORMAT

HH.MI.SSXFF AM TZR

See Also:
Oracle Database Administrator's Guide for information about initialization parameters and initialization parameter files

Viewing NLS Parameter Values

To view the current values of NLS parameters, use the SQL Developer report National Language Support Parameters.

To view the National Language Support Parameters report:

1. From the SQL Developer menu View, select Reports.

2. In the Reports pane, expand Data Dictionary Reports.

3. In the list of reports, expand About Your Database.

4. In the list of reports, select National Language Support Parameters.

5. In the Select Connection window, select hr_conn.

6. Click OK.
The Select Connection window closes and the National Language Support Parameters pane appears, showing the names of the NLS parameters and their current values.

See Also:
Oracle SQL Developer User's Guide for more information about SQL Developer reports

Changing NLS Parameter Values

You can change the value of one or more NLS parameters in any of these ways:

- Change the values for all SQL Developer connections, current and future.

- On the client, change the settings of the corresponding NLS environment variables.
Only on the client, the new values of the NLS environment variables override the values of the corresponding NLS parameters.

You can use environment variables to specify locale-dependent behavior for the client. For example, on a Linux system, this statement sets the value of the NLS_SORT environment variable to FRENCH, overriding the value of the NLS_SORT parameter:

% setenv NLS_SORT FRENCH

Note:
Environment variables might be platform-dependent.

- Change the values only for the current session, using an ALTER SESSION statement with this syntax:

ALTER SESSION SET parameter_name=parameter_value
[ parameter_name=parameter_value ]... ;

Only in the current session, the new values override those set in all of the preceding ways.

You can use the ALTER SESSION to test your application with the settings for different locales.

- Change the values only for the current SQL function invocation.
Only for the current SQL function invocation, the new values override those set in all of the preceding ways.

This section contains:

- Changing NLS Parameter Values for All SQL Developer Connections

- Changing NLS Parameter Values for the Current SQL Function Invocation

See Also:

- Oracle Database SQL Language Reference for more information about the ALTER SESSION statement

- Oracle Database Globalization Support Guide for more information about setting NLS parameters

Changing NLS Parameter Values for All SQL Developer Connections

The following procedure shows how to change the values of NLS parameters for all SQL Developer connections, current and future.

To change National Language Support Parameter values:

1. From the SQL Developer menu Tools, select Preferences.

2. In the Preferences window, in the left frame, expand Database.

3. In the list of database preferences, click NLS.
A list of NLS parameters and their current values appears. The value fields are menus.

4. From the menu to the right of each parameter whose value you want to change, select the desired value.

5. Click OK.
The NLS parameters now have the values that you specified. To verify these values, see "Viewing NLS Parameter Values".

Note:
If the NLS parameter values do not reflect your changes, click the icon Run Report.

See Also:
Oracle SQL Developer User's Guide for more information about SQL Developer preferences

Changing NLS Parameter Values for the Current SQL Function Invocation

SQL functions whose behavior depends on the values of NLS parameters are called locale-dependent. Some locale-dependent SQL functions have optional NLS parameters. These functions are:

- TO_CHAR

- TO_DATE

- TO_NUMBER

- NLS_UPPER

- NLS_LOWER

- NLS_INITCAP

- NLSSORT

In all of the preceding functions, you can specify these NLS parameters:

- NLS_DATE_LANGUAGE

- NLS_DATE_LANGUAGE

- NLS_NUMERIC_CHARACTERS

- NLS_CURRENCY

- NLS_ISO_CURRENCY

- NLS_DUAL_CURRENCY

- NLS_CALENDAR

- NLS_SORT

In the NLSSORT function, you can also specify these NLS parameters:

- NLS_LANGUAGE

- NLS_TERRITORY

- NLS_DATE_FORMAT

To specify NLS parameters in a function, use this syntax:

'parameter=value' ['parameter=value']...

Suppose that you want NLS_DATE_LANGUAGE to be AMERICAN when this query is evaluated:

SELECT last_name FROM employees WHERE hire_date > '01-JAN-1999';

You can set NLS_DATE_LANGUAGE to AMERICAN before running the query:

ALTER SESSION SET NLS_DATE_LANGUAGE=American;
SELECT last_name FROM employees WHERE hire_date > '01-JAN-1999';

Alternatively, you can set NLS_DATE_LANGUAGE to AMERICAN inside the query, using the locale-dependent SQL function TO_DATE with its optional NLS_DATE_LANGUAGE parameter:

SELECT last_name FROM employees
WHERE hire_date > TO_DATE('01-JAN-1999', 'DD-MON-YYYY',
'NLS_DATE_LANGUAGE=AMERICAN');

Tip:
Using session default values for NLS parameters in SQL functions usually results in better performance. Therefore, specify optional NLS parameters in locale-dependent SQL functions only in SQL statements that must not use the default NLS parameter values.

See Also:
Oracle Database Globalization Support Guide for more information about locale-dependent SQL functions with optional NLS parameters

About Individual NLS Parameters

This section contains:

- About Locale and the NLS_LANG Parameter

- About the NLS_LANGUAGE Parameter

- About the NLS_TERRITORY Parameter

- About the NLS_DATE_FORMAT Parameter

- About the NLS_DATE_LANGUAGE Parameter

- About NLS_TIMESTAMP_FORMAT and NLS_TIMESTAMP_TZ_FORMAT Parameters

- About the NLS_CALENDAR Parameter

- About the NLS_NUMERIC_CHARACTERS Parameter

- About the NLS_CURRENCY Parameter

- About the NLS_ISO_CURRENCY Parameter

- About the NLS_DUAL_CURRENCY Parameter

- About the NLS_SORT Parameter

- About the NLS_COMP Parameter

- About the NLS_LENGTH_SEMANTICS Parameter

See Also:

- Oracle Database Globalization Support Guide for more information about setting up a globalization support environment

- "Changing NLS Parameter Values"

About Locale and the NLS_LANG Parameter

A locale is a linguistic and cultural environment in which a system or application runs. The simplest way to specify a locale for Oracle Database Express Edition software is to set the NLS_LANG parameter.

The NLS_LANG parameter sets the default values of the parameters NLS_LANGUAGE and NLS_TERRITORY for both the server session (for example, SQL statement processing) and the client application (for example, display formatting in Oracle Database Express Edition tools). The NLS_LANG parameter also sets the character set that the client application uses for data entered or displayed.

The default value of NLS_LANG is set during database installation. You can use the ALTER SESSION statement to change the values of NLS parameters, including those set by NLS_LANG, for your session. However, only the client can change the NLS settings in the client environment.

See Also:

- Oracle Database Globalization Support Guide for more information about specifying a locale with the NLS_LANG parameter

- Oracle Database Globalization Support Guide for information about languages, territories, character sets, and other locale data supported by Oracle Database

- "About the NLS_LANGUAGE Parameter"

- "About the NLS_TERRITORY Parameter"

- "Changing NLS Parameter Values"

About the NLS_LANGUAGE Parameter

Specifies: Default language of the database. Default conventions for:

- Language for server messages

- Language for names and abbreviations of days and months that are specified in the SQL functions TO_CHAR and TO_DATE

- Symbols for default-language equivalents of AM, PM, AD, and BC

- Default sorting order for character data when the ORDER BY clause is specified

- Writing direction

- Affirmative and negative response strings (for example, YES and NO)

Acceptable Values: Any language name that Oracle supports. For a list, see Oracle Database Globalization Support Guide.

Default Value: Set by NLS_LANG, described in "About Locale and the NLS_LANG Parameter".

Sets default values of:

- NLS_DATE_LANGUAGE, described in "About the NLS_DATE_LANGUAGE Parameter".

- NLS_SORT, described in "About the NLS_SORT Parameter".

Example 7-1 shows how setting NLS_LANGUAGE to ITALIAN and GERMAN affects server messages and month abbreviations.

To try this example in SQL Developer, enter the statements and queries in the Worksheet. For information about the Worksheet, see "Running Queries in SQL Developer". The results shown here are from SQL*Plus; their format is slightly different in SQL Developer.

Example 7-1 NLS_LANGUAGE Affects Server Message and Month Abbreviations

1. Note the current value of NLS_LANGUAGE.

2. If the value in step 1 is not ITALIAN, change it:

ALTER SESSION SET NLS_LANGUAGE=ITALIAN;

3. Query a nonexistent table:

SELECT * FROM nonexistent_table;

Result:

SELECT * FROM nonexistent_table
*
ERROR at line 1:
ORA-00942: tabella o vista inesistente

4. Run this query:

SELECT LAST_NAME, HIRE_DATE
FROM EMPLOYEES
WHERE EMPLOYEE_ID IN (111, 112, 113);

Result:

LAST_NAME                 HIRE_DATE
------------------------- ---------
Sciarra                   30-SET-97
Urman                     07-MAR-98
Popp                      07-DIC-99

3 rows selected.

5. Change the value of NLS_LANGUAGE to GERMAN:

ALTER SESSION SET NLS_LANGUAGE=GERMAN;

6. Repeat the query from step 3.
Result:

SELECT * FROM nonexistent_table
*
ERROR at line 1:
ORA-00942: Tabelle oder View nicht vorhanden

7. Repeat the query from step 4.
Result:

LAST_NAME                 HIRE_DATE
------------------------- ---------
Sciarra                   30-SEP-97
Urman                     07-MRZ-98
Popp                      07-DEZ-99

3 rows selected.

8. Set NLS_LANGUAGE to the value that it had at step 1.

See Also:

- Oracle Database Globalization Support Guide for more information about the NLS_LANGUAGE parameter

- "About Language Support"

- "Changing NLS Parameter Values"

About the NLS_TERRITORY Parameter

Specifies: Default conventions for:

- Date format

- Time stamp format

- Decimal character and group separator

- Local currency symbol

- ISO currency symbol

- Dual currency symbol

Acceptable Values: Any territory name that Oracle supports. For a list, see Oracle Database Globalization Support Guide.

Default Value: Set by NLS_LANG, described in "About Locale and the NLS_LANG Parameter".

Sets default values of:

- NLS_DATE_FORMAT, described in "About the NLS_DATE_FORMAT Parameter".

- NLS_TIMESTAMP_FORMAT and NLS_TIMESTAMP_TZ_FORMAT, described in "About NLS_TIMESTAMP_FORMAT and NLS_TIMESTAMP_TZ_FORMAT Parameters".

- NLS_NUMERIC_CHARACTERS, described in "About the NLS_NUMERIC_CHARACTERS Parameter".

- NLS_CURRENCY, described in "About the NLS_CURRENCY Parameter".

- NLS_ISO_CURRENCY, described in "About the NLS_ISO_CURRENCY Parameter".

- NLS_DUAL_CURRENCY, described in "About the NLS_DUAL_CURRENCY Parameter".

Example 7-2 shows how setting NLS_TERRITORY to JAPAN and AMERICA affects the currency symbol.

To try this example in SQL Developer, enter the statements and queries in the Worksheet. For information about the Worksheet, see "Running Queries in SQL Developer". The results shown here are from SQL*Plus; their format is slightly different in SQL Developer.

Example 7-2 NLS_TERRITORY Affects Currency Symbol

1. Note the current value of NLS_TERRITORY.

2. If the value in step 1 is not JAPAN, change it:

ALTER SESSION SET NLS_TERRITORY=JAPAN;

3. Run this query:

SELECT TO_CHAR(SALARY,'L99G999D99') SALARY
FROM EMPLOYEES
WHERE EMPLOYEE_ID IN (100, 101, 102);

Result:

SALARY
--------------------
¥24,000.00
¥17,000.00
¥17,000.00

3 rows selected.

4. Change the value of NLS_TERRITORY to AMERICA:

ALTER SESSION SET NLS_TERRITORY=AMERICA;

5. Repeat the query from step 3.
Result:

SALARY
--------------------
$24,000.00
$17,000.00
$17,000.00

3 rows selected.

6. Set NLS_TERRITORY to the value that it had at step 1.

See Also:

- Oracle Database Globalization Support Guide for more information about the NLS_TERRITORY parameter

- "About Territory Support"

- "Changing NLS Parameter Values"

About the NLS_DATE_FORMAT Parameter

Specifies: Default date format to use with the TO_CHAR and TO_DATE functions (which are introduced in "Using Conversion Functions in Queries").

Acceptable Values: Any any valid datetime format model. For example:

NLS_DATE_FORMAT='MM/DD/YYYY'

For information about datetime format models, see Oracle Database SQL Language Reference.

Default Value: Set by NLS_TERRITORY, described in "About the NLS_TERRITORY Parameter".

The default date format might not correspond to the convention used in a given territory. To get dates in localized formats, you can use the 'DS' (short date) and 'DL' (long date) formats.

Example 7-3 shows how setting NLS_TERRITORY to AMERICA and FRANCE affects the default, short, and long date formats.

To try this example in SQL Developer, enter the statements and queries in the Worksheet. For information about the Worksheet, see "Running Queries in SQL Developer". The results shown here are from SQL*Plus; their format is slightly different in SQL Developer.

Example 7-3 NLS_TERRITORY Affects Date Formats

1. Note the current value of NLS_TERRITORY.

2. If the value in step 1 is not AMERICA, change it:

ALTER SESSION SET NLS_TERRITORY=AMERICA;

3. Run this query:

SELECT hire_date "Default",
TO_CHAR(hire_date,'DS') "Short",
TO_CHAR(hire_date,'DL') "Long"
FROM employees
WHERE employee_id IN (111, 112, 113);

Result:

Default    Short      Long
--------- ---------- -----------------------------
30-SEP-05 9/30/2005  Friday, September 30, 2005
07-MAR-98 3/7/2006   Tuesday, March 07, 2006
07-DEC-99 12/7/2007  Friday, December 07, 2007

3 rows selected.

4. Change the value of NLS_TERRITORY to FRANCE:

ALTER SESSION SET NLS_TERRITORY=FRANCE;

5. Repeat the query from step 3.
Result:

Default  Short      Long
-------- ---------- ---------------------------
30/09/05 30/09/2005 friday 30 september 2005
07/03/06 07/03/2006 tuesday 7 march 2006
07/12/07 07/12/2007 friday 7 december 2007

3 rows selected.

(To get the names of the days and months in French, you must set either NLS_LANGUAGE or NLS_DATE_LANGUAGE to FRENCH before running the query.)

6. Set NLS_TERRITORY to the value that it had at step 1.

Example 7-4 changes the value of NLS_DATE_FORMAT, overriding the default value set by NLS_TERRITORY.

To try this example in SQL Developer, enter the statements and queries in the Worksheet. For information about the Worksheet, see "Running Queries in SQL Developer". The results shown here are from SQL*Plus; their format is slightly different in SQL Developer.

Example 7-4 NLS_DATE_FORMAT Overrides NLS_TERRITORY

1. Note the current values of NLS_TERRITORY and NLS_DATE_FORMAT.

2. If the value of NLS_TERRITORY in step 1 is not AMERICA, change it:

ALTER SESSION SET NLS_TERRITORY=AMERICA;

3. If the value of NLS_DATE_FORMAT in step 1 is not 'Day Month ddth', change it:

ALTER SESSION SET NLS_DATE_FORMAT='Day Month ddth';

4. Run this query (from previous example, step 3):

SELECT hire_date "Default",
TO_CHAR(hire_date,'DS') "Short",
TO_CHAR(hire_date,'DL') "Long"
FROM employees
WHERE employee_id IN (111, 112, 113);

Result:

Default                  Short      Long
------------------------ ---------- -----------------------------
Friday    September 30th 9/30/2005  Tuesday, September 30, 2005
Tuesday   March     07th 3/7/2006   Saturday, March 07, 2006
Friday    December  07th 12/7/2007  Tuesday, December 07, 2007

3 rows selected.

5. Set NLS_TERRITORY and NLS_DATE_FORMAT to the values that they had at step 1.

See Also:

- Oracle Database Globalization Support Guide for more information about the NLS_DATE_FORMAT parameter

- Oracle Database SQL Language Reference for more information about the TO_CHAR function

- Oracle Database SQL Language Reference for more information about the TO_DATE function

- "About Date and Time Formats"

- "Changing NLS Parameter Values"

About the NLS_DATE_LANGUAGE Parameter

Specifies: Language for names and abbreviations of days and months that are produced by:

- SQL functions TO_CHAR and TO_DATE (which are introduced in "Using Conversion Functions in Queries")

- Default date format (set by NLS_DATE_FORMAT, described in "About the NLS_DATE_FORMAT Parameter")

- Symbols for default-language equivalents of AM, PM, AD, and BC

Acceptable Values: Any language name that Oracle supports. For a list, see Oracle Database Globalization Support Guide.

Default Value: Set by NLS_LANGUAGE, described in "About the NLS_LANGUAGE Parameter".

Example 7-5 shows how setting NLS_DATE_LANGUAGE to FRENCH and SWEDISH affects the displayed system date.

To try this example in SQL Developer, enter the statements and queries in the Worksheet. For information about the Worksheet, see "Running Queries in SQL Developer". The results shown here are from SQL*Plus; their format is slightly different in SQL Developer.

Example 7-5 NLS_DATE_LANGUAGE Affects Displayed SYSDATE

1. Note the current value of NLS_DATE_LANGUAGE.

2. If the value of NLS_DATE_LANGUAGE in step 1 is not FRENCH, change it:

ALTER SESSION SET NLS_DATE_LANGUAGE=FRENCH;

3. Run this query:

SELECT TO_CHAR(SYSDATE, 'Day:Dd Month yyyy') "System Date"
FROM DUAL;

Result:

System Date
--------------------------
Vendredi:28 December   2012

4. Change the value of NLS_DATE_LANGUAGE to SWEDISH:

ALTER SESSION SET NLS_DATE_LANGUAGE=SWEDISH;

5. Repeat the query from step 3.
Result:

System Date
-------------------------
Fredag :28 December   2012

6. Set NLS_DATE_LANGUAGE to the value that it had at step 1.

See Also:

- Oracle Database Globalization Support Guide for more information about the NLS_DATE_LANGUAGE parameter

- Oracle Database SQL Language Reference for more information about the TO_CHAR function

- Oracle Database SQL Language Reference for more information about the TO_DATE function

- "About Date and Time Formats"

- "Changing NLS Parameter Values"

About NLS_TIMESTAMP_FORMAT and NLS_TIMESTAMP_TZ_FORMAT Parameters

Specify: Default date format for:

- TIMESTAMP audiotape

- TIMESTAMP WITH LOCAL TIME ZONE audiotape

Acceptable Values: Any any valid datetime format model. For example:

NLS_TIMESTAMP_FORMAT='YYYY-MM-DD HH:MI:SS.FF'
NLS_TIMESTAMP_TZ_FORMAT='YYYY-MM-DD HH:MI:SS.FF TZH:TZM'

For information about datetime format models, see Oracle Database SQL Language Reference.

Default Value: Set by NLS_TERRITORY, described in "About the NLS_TERRITORY Parameter".

See Also:

- Oracle Database Globalization Support Guide for more information about the NLS_TIMESTAMP_FORMAT parameter

- Oracle Database Globalization Support Guide for more information about the NLS_TIMESTAMP_TZ_FORMAT parameter

- Oracle Database Globalization Support Guide for information about date/time data types and time zone support

- Oracle Database SQL Language Reference for more information about the TIMESTAMP audiotape

- Oracle Database SQL Language Reference for more information about the TIMESTAMP WITH LOCAL TIME ZONE data type

- "About Date and Time Formats"

- "Changing NLS Parameter Values"

About the NLS_CALENDAR Parameter

Specifies: Calendar system for the database.

Acceptable Values: Any calendar system that Oracle supports. For a list, see Oracle Database Globalization Support Guide.

Default Value: Gregorian

Example 7-6 shows how setting NLS_CALENDAR to 'English Hijrah' and Gregorian affects the displayed system date.

To try this example in SQL Developer, enter the statements and queries in the Worksheet. For information about the Worksheet, see "Running Queries in SQL Developer". The results shown here are from SQL*Plus; their format is slightly different in SQL Developer.

Example 7-6 NLS_CALENDAR Affects Displayed SYSDATE

1. Note the current value of NLS_CALENDAR.

2. If the value of NLS_CALENDAR in step 1 is not 'English Hijrah', change it:

ALTER SESSION SET NLS_CALENDAR='English Hijrah';

3. Run this query:

SELECT SYSDATE FROM DUAL;

Result:

SYSDATE
-------------------------
17 Safar             1434

4. Change the value of NLS_CALENDAR to 'Gregorian':

ALTER SESSION SET NLS_CALENDAR='Gregorian';

5. Run this query:

SELECT SYSDATE FROM DUAL;

Result:

SYSDATE
---------
31-DEC-12

6. Set NLS_CALENDAR to the value that it had at step 1.

See Also:

- Oracle Database Globalization Support Guide for more information about the NLS_CALENDAR parameter

- "About Calendar Formats"

- "Changing NLS Parameter Values"

About the NLS_NUMERIC_CHARACTERS Parameter

Specifies: Decimal character (which separates the integer and decimal parts of a number) and group separator (which separates integer groups to show thousands and millions, for example). The group separator is the character returned by the numeric format element G.

Acceptable Values: Any two different single-byte characters except:

- A numeric character

- Plus (+)

- Minus (-)

- Less than (<)

- Greater than (>)

Default Value: Set by NLS_TERRITORY, described in "About the NLS_TERRITORY Parameter".

In a SQL statement, you can represent a number as either:

- Numeric literal
A numeric literal is not enclosed in quotation marks, always uses a period (.) as the decimal character, and never contains a group separator.

- Text literal
A text literal is enclosed in single quotation marks. It is implicitly or explicitly converted to a number, if required, according to the current NLS settings.

Example 7-7 shows how two different NLS_NUMERIC_CHARACTERS settings affect the displayed result of the same query.

To try this example in SQL Developer, enter the statements and queries in the Worksheet. For information about the Worksheet, see "Running Queries in SQL Developer". The results shown here are from SQL*Plus; their format is slightly different in SQL Developer.

Example 7-7 NLS_NUMERIC_CHARACTERS Affects Decimal Character and Group Separator

1. Note the current value of NLS_NUMERIC_CHARACTERS.

2. If the value of NLS_NUMERIC_CHARACTERS in step 1 is not ",." (decimal character is comma and group separator is period), change it:

ALTER SESSION SET NLS_NUMERIC_CHARACTERS=",.";

3. Run this query:

SELECT TO_CHAR(4000, '9G999D99') "Number" FROM DUAL;

Result:

Number
---------
4.000,00

4. Change the value of NLS_NUMERIC_CHARACTERS to ",." (decimal character is period and group separator is comma):

ALTER SESSION SET NLS_NUMERIC_CHARACTERS=".,";

5. Run this query:

SELECT TO_CHAR(4000, '9G999D99') "Number" FROM DUAL;

Result:

Number
---------
4,000.00

6. Set NLS_NUMERIC_CHARACTERS to the value that it had at step 1.

See Also:

- Oracle Database Globalization Support Guide for more information about the NLS_NUMERIC_CHARACTERS parameter

- "About Numeric and Monetary Formats"

- "Changing NLS Parameter Values"

About the NLS_CURRENCY Parameter

Specifies: Local currency symbol (the character string returned by the numeric format element L).

Acceptable Values: Any valid currency symbol string.

Default Value: Set by NLS_TERRITORY, described in "About the NLS_TERRITORY Parameter".

Example 7-8 changes the value of NLS_CURRENCY, overriding the default value set by NLS_TERRITORY.

To try this example in SQL Developer, enter the statements and queries in the Worksheet. For information about the Worksheet, see "Running Queries in SQL Developer". The results shown here are from SQL*Plus; their format is slightly different in SQL Developer.

Example 7-8 NLS_CURRENCY Overrides NLS_TERRITORY

1. Note the current values of NLS_TERRITORY and NLS_CURRENCY.

2. If the value of NLS_TERRITORY in step 1 is not AMERICA, change it:

ALTER SESSION SET NLS_TERRITORY=AMERICA;

3. Run this query:

SELECT TO_CHAR(salary, 'L099G999D99') "Salary"
FROM EMPLOYEES
WHERE salary > 13000;

Result:

Salary
---------------------
$024,000.00
$017,000.00
$017,000.00
$014,000.00
$013,500.00

4. Change the value of NLS_CURRENCY to '¥':

ALTER SESSION SET NLS_CURRENCY='¥';

5. Run this query:

SELECT TO_CHAR(salary, 'L099G999D99') "Salary"
FROM EMPLOYEES
WHERE salary > 13000;

Result:

Salary
---------------------
¥024,000.00
¥017,000.00
¥017,000.00
¥014,000.00
¥013,500.00

6. Set NLS_TERRITORY and NLS_CURRENCY to the values that they had at step 1.

See Also:

- Oracle Database Globalization Support Guide for more information about the NLS_CURRENCY parameter

- "About Numeric and Monetary Formats"

- "Changing NLS Parameter Values"

About the NLS_ISO_CURRENCY Parameter

Specifies: ISO currency symbol (the character string returned by the numeric format element C).

Acceptable Values: Any valid currency symbol string.

Default Value: Set by NLS_TERRITORY, described in "About the NLS_TERRITORY Parameter".

Local currency symbols can be ambiguous, but ISO currency symbols are unique.

Example 7-9 shows that the territories AUSTRALIA and AMERICA have the same local currency symbol, but different ISO currency symbols.

To try this example in SQL Developer, enter the statements and queries in the Worksheet. For information about the Worksheet, see "Running Queries in SQL Developer". The results shown here are from SQL*Plus; their format is slightly different in SQL Developer.

Example 7-9 NLS_ISO_CURRENCY

1. Note the current values of NLS_TERRITORY and NLS_ISO_CURRENCY.

2. If the value of NLS_TERRITORY in step 1 is not AUSTRALIA, change it:

ALTER SESSION SET NLS_TERRITORY=AUSTRALIA;

3. Run this query:

SELECT TO_CHAR(salary, 'L099G999D99') "Local",
TO_CHAR(salary, 'C099G999D99') "ISO"
FROM EMPLOYEES
WHERE salary > 15000;

Result:

Local                 ISO
--------------------- ------------------
$024,000.00      AUD024,000.00
$017,000.00      AUD017,000.00
$017,000.00      AUD017,000.00

4. Change the value of NLS_TERRITORY to AMERICA:

ALTER SESSION SET NLS_TERRITORY=AMERICA;

5. Run this query:

SELECT TO_CHAR(salary, 'L099G999D99') "Local",
TO_CHAR(salary, 'C099G999D99') "ISO"
FROM EMPLOYEES
WHERE salary > 15000;

Result:

Local                 ISO
--------------------- ------------------
$024,000.00      USD024,000.00
$017,000.00      USD017,000.00
$017,000.00      USD017,000.00

6. Set NLS_TERRITORY and NLS_ISO_CURRENCY to the values that they had at step 1.

See Also:

- Oracle Database Globalization Support Guide for more information about the NLS_ISO_CURRENCY parameter

- "About Numeric and Monetary Formats"

- "Changing NLS Parameter Values"

About the NLS_DUAL_CURRENCY Parameter

Specifies: Dual currency symbol (introduced to support the euro currency symbol during the euro transition period).

Acceptable Values: Any valid currency symbol string.

Default Value: Set by NLS_TERRITORY, described in "About the NLS_TERRITORY Parameter".

See Also:

- Oracle Database Globalization Support Guide for more information about the NLS_DUAL_CURRENCY parameter

- "About Numeric and Monetary Formats"

- "Changing NLS Parameter Values"

About the NLS_SORT Parameter

Specifies: Linguistic sort order (collating sequence) for queries that have the ORDER BY clause.

Acceptable Values:

- BINARY
Sort order is based on the binary sequence order of either the database character set or the national character set, depending on the data type.

- Any linguistic sort name that Oracle supports
Sort order is based on the order of the specified linguistic sort name. The linguistic sort name is usually the same as the language name, but not always. For a list of supported linguistic sort names, see Oracle Database Globalization Support Guide.

Default Value: Set by NLS_LANGUAGE, described in "About the NLS_LANGUAGE Parameter".

Example 7-10 shows how two different NLS_SORT settings affect the displayed result of the same query. The settings are BINARY and Traditional Spanish (SPANISH_M). Traditional Spanish treats ch, ll, and ñ as letters that follow c, l, and n, respectively.

To try this example in SQL Developer, enter the statements and queries in the Worksheet. For information about the Worksheet, see "Running Queries in SQL Developer". The results shown here are from SQL*Plus; their format is slightly different in SQL Developer.

Example 7-10 NLS_SORT Affects Linguistic Sort Order

1. Create table for Spanish words:

CREATE TABLE temp (name VARCHAR2(15));

2. Populate table with some Spanish words:

INSERT INTO temp (name) VALUES ('laguna');
INSERT INTO temp (name) VALUES ('llama');
INSERT INTO temp (name) VALUES ('loco');

3. Note the current value of NLS_SORT.

4. If the value of NLS_SORT in step 3 is not BINARY, change it:

ALTER SESSION SET NLS_SORT=BINARY;

5. Run this query:

SELECT * FROM temp ORDER BY name;

Result:

NAME
---------------
laguna
llama
loco

6. Change the value of NLS_SORT to SPANISH_M (Traditional Spanish):

ALTER SESSION SET NLS_SORT=SPANISH_M;

7. Repeat the query from step 5.
Result:

NAME
---------------
laguna
loco
llama

8. Drop the table:

DROP TABLE temp;

9. Set NLS_SORT to the value that it had at step 3.

Case-Insensitive and Accent-Insensitive Sorts

Operations inside Oracle Database Express Edition are sensitive to the case and the accents of the characters. To perform a case-insensitive sort, append _CI to the value of the NLS_SORT parameter (for example, BINARY_CI or XGERMAN_CI). To perform a sort that is both case-insensitive and accent-insensitive, append _AI to the value of the NLS_SORT parameter (for example, BINARY_AI or FRENCH_M_AI).

See Also:

- Oracle Database Globalization Support Guide for more information about the NLS_SORT parameter

- Oracle Database Globalization Support Guide for more information about case-insensitive and accent-insensitive sorts

- "About Linguistic Sorting and String Searching"

- "Changing NLS Parameter Values"

About the NLS_COMP Parameter

Specifies: Character comparison behavior of SQL operations.

Acceptable Values:

- BINARY
SQL compares the binary codes of characters. One character is greater than another if it has a higher binary code.

- LINGUISTIC
SQL performs a linguistic comparison based on the value of the NLS_SORT parameter, described in "About the NLS_SORT Parameter".

- ANSI
This value is provided only for backward compatibility.

Default Value: BINARY

Example 7-11 shows that the result of a query can depend on the NLS_COMP setting.

To try this example in SQL Developer, enter the statements and queries in the Worksheet. For information about the Worksheet, see "Running Queries in SQL Developer". The results shown here are from SQL*Plus; their format is slightly different in SQL Developer.

Example 7-11 NLS_COMP Affects SQL Character Comparison

1. Note the current values of NLS_SORT and NLS_COMP.

2. If the values of NLS_SORT and NLS_COMP in step 1 are not SPANISH_M (Traditional Spanish) and BINARY, respectively, change them:

ALTER SESSION SET NLS_SORT=SPANISH_M NLS_COMP=BINARY;

3. *Run this query:

SELECT LAST_NAME FROM EMPLOYEES
WHERE LAST_NAME LIKE 'C%';

Result:

LAST_NAME
-------------------------
Cabrio
Cambrault
Cambrault
Chen
Chung
Colmenares

6 rows selected

4. Change the value of NLS_COMP to LINGUISTIC:

ALTER SESSION SET NLS_COMP=LINGUISTIC;

5. Repeat the query from step 3.
Result:

LAST_NAME
-------------------------
Cabrio
Cambrault
Cambrault
Colmenares

4 rows selected

This time, Chen and Chung are not returned because Traditional Spanish treats ch as a single character that follows c.

6. Set NLS_SORT and NLS_COMP to the values that they had in step 1.

See Also:

- Oracle Database Globalization Support Guide for more information about the NLS_COMP parameter

- "About Linguistic Sorting and String Searching"

- "Changing NLS Parameter Values"

About the NLS_LENGTH_SEMANTICS Parameter

Specifies: Length semantics for columns of the character data types CHAR, VARCHAR2, and LONG; that is, whether these columns are specified in bytes or in characters. (Applies only to columns that are declared after the parameter is set.)

Acceptable Values:

- BYTE
New CHAR, VARCHAR2, and LONG columns are specified in bytes.

- CHAR
New CHAR, VARCHAR2, and LONG columns are specified in characters.

Default Value: BYTE

To try this example in SQL Developer, enter the statements and queries in the Worksheet. For information about the Worksheet, see "Running Queries in SQL Developer". The results shown here are from SQL*Plus; their format is slightly different in SQL Developer.

Example 7-12 NLS_LENGTH_SEMANTICS Affects Storage of VARCHAR2 Column

1. Note the current values of NLS_LENGTH_SEMANTICS.

2. If the value of NLS_LENGTH_SEMANTICS in step 1 is not BYTE, change it:

ALTER SESSION SET NLS_LENGTH_SEMANTICS=BYTE;

3. Create a table with a VARCHAR2 column:

CREATE TABLE SEMANTICS_BYTE(SOME_DATA VARCHAR2(20));

4. Click the tab Connections.

5. In the Connections frame, expand hr_conn.

6. In the list of schema object types, expand Tables.

7. In the list of tables, select SEMANTICS_BYTE.
To the right of the Connections frame, the Columns pane shows that for Column Name SOME_DATA, the Data Type is VARCHAR2(20 BYTE).

8. Change the value of NLS_LENGTH_SEMANTICS to CHAR:

ALTER SESSION SET NLS_LENGTH_SEMANTICS=CHAR;

9. Create another table with a VARCHAR2 column:

CREATE TABLE SEMANTICS_CHAR(SOME_DATA VARCHAR2(20));

10. In the Connections frame, click the Refresh icon.
The list of tables now includes SEMANTICS_CHAR.

11. Select SEMANTICS_CHAR.
The Columns pane shows that for Column Name SOME_DATA, the Data Type is VARCHAR2(20 CHAR).

12. Select SEMANTICS_BYTE again.
The Columns pane shows that for Column Name SOME_DATA, the Data Type is still VARCHAR2(20 BYTE).

13. Set the value of NLS_LENGTH_SEMANTICS to the value that it had in step 1.

See Also:

- Oracle Database Globalization Support Guide for more information about the NLS_LENGTH_SEMANTICS parameter

- "About Length Semantics"

- "Changing NLS Parameter Values"

Using Unicode in Globalized Applications

You can insert and retrieve Unicode data. Data is transparently converted among the database and client programs, which ensures that client programs are independent of the database character set and national character set.

This section contains:

- Representing Unicode String Literals in SQL and PL/SQL

- Avoiding Data Loss During Character-Set Conversion

See Also:

- Oracle Database Globalization Support Guide for more information about SQL and PL/SQL programming with Unicode

- Oracle Database Globalization Support Guide for general information about programming with Unicode

Representing Unicode String Literals in SQL and PL/SQL

There are three ways to represent a Unicode string literal in SQL or PL/SQL:

- N'string'
Example: N'résumé'.

Limitations: See "Avoiding Data Loss During Character-Set Conversion".

- NCHR(number)
The SQL function NCHR returns the character whose binary equivalent is number in the national character set. The character returned has data type NVARCHAR2.

Example: NCHR(36) represents $ in the default national character set, AL16UTF16.

Limitations: Portability of the value of NCHR(number) is limited to applications that use the same national character set.

- UNISTR('string')
The SQL function UNISTR converts string to the national character set.

For portability and data preservation, Oracle recommends that string contain only ASCII characters and Unicode encoding values. A Unicode encoding value has the form \xxxx, where xxxx is the hexadecimal value of a character code value in UCS-2 encoding format.

Example: UNISTR('G\0061ry') represents 'Gary'

ASCII characters are converted to the database character set and then to the national character set. Unicode encoding values are converted directly to the national character set.

See Also:

- Oracle Database Globalization Support Guide for more information about Unicode string literals

- Oracle Database SQL Language Reference for more information about the NCHR function

- Oracle Database SQL Language Reference for more information about the UNISTR function

Avoiding Data Loss During Character-Set Conversion

As part of a SQL or PL/SQL statement, a literal (with or without the prefix N) is encoded in the same character set as the rest of the statement. On the client side, the statement is encoded in the client character set, which is determined by the NLS_LANG parameter. On the server side, the statement is encoded in the database character set.

When the SQL or PL/SQL statement is transferred from the client to the database, its character set is converted accordingly. If the database character set does not contain all characters that the client used in the text literals, then data is lost in this conversion. NCHAR string literals are more vulnerable than CHAR text literals, because they are designed to be independent of the database character set.

To avoid data loss in conversion to an incompatible database character set, you can activate the NCHAR literal replacement functionality. For more information, see Oracle Database Globalization Support Guide.

8 Building Effective Applications

This chapter contains:

- Building Scalable Applications

- Recommended Programming Practices

- Recommended Security Practices

See Also:
Oracle Database Advanced Application Developer's Guide for more information about creating and deploying applications that are optimized for Oracle Database Express Edition

Building Scalable Applications

This section contains:

- About Scalable Applications

- Using Bind Arguments to Improve Scalability

- Using PL/SQL to Improve Scalability

- About Concurrency and Scalability

- Limiting the Number of Concurrent Sessions

- Comparing Programming Techniques with Runstats

About Scalable Applications

A scalable application can process a larger workload with a proportional increase in system resource usage. For example, if you double its workload, a scalable application uses twice as many system resources.

An unscalable application exhausts a system resource; therefore, if you increase the application workload, no more throughput is possible. Unscalable applications result in fixed throughputs and poor response times.

Examples of resource exhaustion are:

- Hardware exhaustion

- Table scans in high-volume transactions causing inevitable disk input/output (I/O) shortages

- Excessive network requests causing network and scheduling bottlenecks

- Memory allocation causing paging and swapping

- Excessive process and thread allocation causing operating system thrashing

Design your applications to use the same resources, regardless of user populations and data volumes, and not to overload system resources.

Using Bind Arguments to Improve Scalability

Bind arguments, used correctly, let you develop efficient, scalable applications.

Just as a subprogram can have parameters, whose values are supplied by the invoker, a SQL statement can have bind argument placeholders, whose values (called bind arguments) are supplied at runtime. Just as a subprogram is compiled once and then run many times with different parameters, a SQL statement with bind argument placeholders is hard parsed once and then soft parsed with different bind arguments.

A hard parse, which includes optimization and row source generation, is a very CPU-intensive operation. A soft parse, which skips optimization and row source generation and proceeds straight to execution, is usually much faster than a hard parse of the same statement. (For an overview of SQL processing, which includes the difference between a hard and soft parse, see Oracle Database Concepts.)

Not only is a hard parse a CPU-intensive operation, it is an unscalable operation, because it cannot be done concurrently with many other operations. For more information about concurrency and scalability, see "About Concurrency and Scalability".

Example 8-1 shows the performance difference between a query without a bind variable and a semantically equivalent query with a bind variable. The former is slower and uses many more latches (for information about how latches affect scalability, see "About Latches and Concurrency"). To collect and display performance statistics, the example uses the Runstats tool, described in "Comparing Programming Techniques with Runstats".

Note:

- Example 8-1 shows the performance cost for a single user. As more users are added, the cost escalates rapidly.

- The result of Example 8-1 was produced with this setting:

SET SERVEROUTPUT ON FORMAT TRUNCATED

Example 8-1 Bind Variable Improves Performance

CREATE TABLE t ( x VARCHAR2(5) );

DECLARE
TYPE rc IS REF CURSOR;
l_cursor rc;
BEGIN
runstats_pkg.rs_start;  -- Collect statistics for query without bind variable

FOR i IN 1 .. 5000 LOOP
OPEN l_cursor FOR 'SELECT x FROM t WHERE x = ' || TO_CHAR(i);
CLOSE l_cursor;
END LOOP;

runstats_pkg.rs_middle;  -- Collect statistics for query with bind variable

FOR i IN 1 .. 5000 LOOP
OPEN l_cursor FOR 'SELECT x FROM t WHERE x = :x' USING i;
CLOSE l_cursor;
END LOOP;

runstats_pkg.rs_stop(500);  -- Stop collecting statistics
end;
/

Result is similar to:

Run 1 ran in 740 hsec
Run 2 ran in 30 hsec
Run 1 ran in 2466.67% of the time of run 2

Name                                   Run 1         Run 2    Difference
STAT...recursive cpu usage               729            19          -710
STAT...CPU used by this sessio           742            30          -712
STAT...parse time elapsed              1,051             4        -1,047
STAT...parse time cpu                  1,066             2        -1,064
STAT...session cursor cache hi             1         4,998         4,997
STAT...table scans (short tabl         5,000             1        -4,999
STAT...parse count (total)            10,003         5,004        -4,999
LATCH.session idle bit                 5,003             3        -5,000
LATCH.session allocation               5,003             3        -5,000
STAT...execute count                  10,003         5,003        -5,000
STAT...opened cursors cumulati        10,003         5,003        -5,000
STAT...parse count (hard)             10,001             5        -9,996
STAT...CCursor + sql area evic        10,000             1        -9,999
STAT...enqueue releases               10,008             7       -10,001
STAT...enqueue requests               10,009             7       -10,002
STAT...calls to get snapshot s        20,005         5,006       -14,999
STAT...calls to kcmgcs                20,028            35       -19,993
STAT...consistent gets pin (fa        20,013            17       -19,996
LATCH.call allocation                 20,002             6       -19,996
STAT...consistent gets from ca        20,014            18       -19,996
STAT...consistent gets                20,014            18       -19,996
STAT...consistent gets pin            20,013            17       -19,996
LATCH.simulator hash latch            20,014            11       -20,003
STAT...session logical reads          20,080            75       -20,005
LATCH.shared pool simulator           20,046             5       -20,041
LATCH.enqueue hash chains             20,343            15       -20,328
STAT...recursive calls                40,015        15,018       -24,997
LATCH.cache buffers chains            40,480           294       -40,186
STAT...session pga memory max        131,072        65,536       -65,536
STAT...session pga memory            131,072        65,536       -65,536
LATCH.row cache objects              165,209           139      -165,070
STAT...session uga memory max        219,000             0      -219,000
LATCH.shared pool                    265,108           152      -264,956
STAT...logical read bytes from   164,495,360       614,400  -163,880,960

Run 1 latches total compared to run 2 -- difference and percentage
Run 1         Run 2          Diff       Pct
562,092           864      -561,228  2,466.67%

PL/SQL procedure successfully completed.

Note:

- Using bind arguments instead of string literals is the most effective way to make your code invulnerable to SQL injection attacks. For details, see Oracle Database PL/SQL Language Reference.

- Bind arguments sometimes reduce the efficiency of data warehousing systems. Because most queries take so long, the optimizer tries to produce the best plan for each query rather than the best generic query. Using bind arguments sometimes forces the optimizer to produce the best generic query. For information about improving performance in data warehousing systems, see Oracle Database Data Warehousing Guide.

Although soft parsing is more efficient than hard parsing, the cost of soft parsing a statement many times is still very high. To maximize the efficiency and scalability of your application, minimize parsing. The easiest way to minimize parsing is to use PL/SQL.

Using PL/SQL to Improve Scalability

This section contains:

- How PL/SQL Minimizes Parsing

- About the EXECUTE IMMEDIATE Statement

- About the DBMS_SQL Package

- About Bulk SQL

How PL/SQL Minimizes Parsing

PL/SQL, which is optimized for database access, silently caches statements. In PL/SQL, when you close a cursor, the cursor closes from your perspective—that is, you cannot use it where an open cursor is required—but PL/SQL actually keeps the cursor open and caches its statement. If you use the cached statement again, PL/SQL uses the same cursor, thereby avoiding a parse. (PL/SQL closes cached statements if necessary—for example, if your program must open another cursor but doing so would exceed the init.ora setting of OPEN_CURSORS.)

PL/SQL can silently cache only SQL statements that cannot change at runtime.

About the EXECUTE IMMEDIATE Statement

The basic syntax of the EXECUTE IMMEDIATE statement is:

EXECUTE IMMEDIATE sql_statement

sql_statement is a string that represents a SQL statement. If sql_statement has the same value every time the EXECUTE IMMEDIATE statement runs, then PL/SQL can cache the EXECUTE IMMEDIATE statement. If sql_statement can be different every time the EXECUTE IMMEDIATE statement runs, then PL/SQL cannot cache the EXECUTE IMMEDIATE statement.

See Also:

- Oracle Database PL/SQL Language Reference for information about EXECUTE IMMEDIATE

- "About the DBMS_SQL Package"

About OPEN FOR Statements

The basic syntax of the OPEN FOR statement is:

OPEN cursor_variable FOR query

Your application can open cursor_variable for several different queries before closing it. Because PL/SQL cannot determine the number of different queries until runtime, PL/SQL cannot cache the OPEN FOR statement.

If you do not need to use a cursor variable, then use a declared cursor, for both better performance and ease of programming. For details, see Oracle Database Advanced Application Developer's Guide.

See Also:

- Oracle Database PL/SQL Language Reference for information about OPEN FOR

- "About Cursor Variables"

- "About Cursors"

About the DBMS_SQL Package

The DBMS_SQL package is an API for building, running, and describing dynamic SQL statements. Using the DBMS_SQL package takes more effort than using the EXECUTE IMMEDIATE statement, but you must use the DBMS_SQL package if the PL/SQL compiler cannot determine at compile time the number or types of output host variables (select list items) or input bind variables.

See Also:

- Oracle Database PL/SQL Language Reference for more information about when to use the DBMS_SQL package

- Oracle Database PL/SQL Packages and Types Reference for complete information about the DBMS_SQL package

- "About the EXECUTE IMMEDIATE Statement"

About Bulk SQL

Bulk SQL reduces the number of "round trips" between PL/SQL and SQL, thereby using fewer resources. Without bulk SQL, you retrieve one row at a time from the database (SQL), process it (PL/SQL), and return it to the database (SQL). With bulk SQL, you retrieve a set of rows from the database, process the set of rows, and then return the whole set to the database.

Oracle recommends using Bulk SQL when you retrieve multiple rows from the database and return them to the database, as in Example 8-2. You do not need bulk SQL if you retrieve multiple rows but do not return them; for example:

FOR x IN (SELECT * FROM t WHERE ... )  -- Retrieve row set (implicit array fetch)
LOOP
DBMS_OUTPUT.PUT_LINE(t.x);          -- Process rows but do not return them
END LOOP;

Example 8-2 loops through a table t with a column object_name, retrieving sets of 100 rows, processing them, and returning them to the database. (Limiting the bulk FETCH statement to 100 rows requires an explicit cursor.)

Example 8-2 Bulk SQL

CREATE OR REPLACE PROCEDURE bulk AS
TYPE ridArray IS TABLE OF ROWID;
TYPE onameArray IS TABLE OF t.object_name%TYPE;

CURSOR c is SELECT ROWID rid, object_name  -- explicit cursor
FROM t t_bulk;

l_rids    ridArray;
l_onames  onameArray;
N         NUMBER := 100;
BEGIN
OPEN c;
LOOP
FETCH c BULK COLLECT
INTO l_rids, l_onames LIMIT N;   -- retrieve N rows from t

FOR i in 1 .. l_rids.COUNT
LOOP                           -- process N rows
l_onames(i) := substr(l_onames(i),2) || substr(l_onames(i),1,1);
END LOOP;

FORALL i in 1 .. l_rids.count  -- return processed rows to t
UPDATE t
SET object_name = l_onames(i)
WHERE ROWID = l_rids(i);
EXIT WHEN c%NOTFOUND;
END LOOP;
CLOSE c;
END;
/

Example 8-3 does the same job as Example 8-2, without bulk SQL.

Example 8-3 Without Bulk SQL

CREATE OR REPLACE PROCEDURE slow_by_slow AS
BEGIN
FOR x IN (SELECT rowid rid, object_name FROM t t_slow_by_slow)
LOOP
x.object_name := substr(x.object_name,2) || substr(x.object_name,1,1);

UPDATE t
SET object_name = x.object_name
WHERE rowid = x.rid;
END LOOP;
END;

As these TKPROF reports for Example 8-2 and Example 8-3 show, using bulk SQL for this job uses almost 50% less CPU time:

SELECT ROWID RID, OBJECT_NAME FROM T T_BULK

call     count       cpu    elapsed       disk      query    current        rows
------- ------  -------- ---------- ---------- ---------- ----------  ----------
total      721      0.17       0.17          0      22582          0       71825
********************************************************************************
UPDATE T SET OBJECT_NAME = :B1 WHERE ROWID = :B2

call     count       cpu    elapsed       disk      query    current        rows
------- ------  -------- ---------- ---------- ---------- ----------  ----------
Parse        1      0.00       0.00          0          0          0           0
Execute    719     12.83      13.77          0      71853      74185       71825
Fetch        0      0.00       0.00          0          0          0           0
------- ------  -------- ---------- ---------- ---------- ----------  ----------
total      720     12.83      13.77          0      71853      74185       71825

SELECT ROWID RID, OBJECT_NAME FROM T T_SLOW_BY_SLOW

call     count       cpu    elapsed       disk      query    current        rows
------- ------  -------- ---------- ---------- ---------- ----------  ----------
total      721      0.17       0.17          0      22582          0       71825
********************************************************************************
UPDATE T SET OBJECT_NAME = :B2 WHERE ROWID = :B1

call     count       cpu    elapsed       disk      query    current        rows
------- ------  -------- ---------- ---------- ---------- ----------  ----------
Parse        1      0.00       0.00          0          0          0           0
Execute  71824     21.25      22.25          0      71836      73950       71824
Fetch        0      0.00       0.00          0          0          0           0
------- ------  -------- ---------- ---------- ---------- ----------  ----------
total    71825     21.25      22.25          0      71836      73950       71824

However, using bulk SQL for this job uses more CPU time—and more code—than using a single SQL statement, as this TKPROF report shows:

UPDATE T SET OBJECT_NAME = SUBSTR(OBJECT_NAME,2) || SUBSTR(OBJECT_NAME,1,1)

call     count       cpu    elapsed       disk      query    current        rows
------- ------  -------- ---------- ---------- ---------- ----------  ----------
Parse        1      0.00       0.00          0          0          0           0
Execute      1      1.30       1.44          0       2166      75736       71825
Fetch        0      0.00       0.00          0          0          0           0
------- ------  -------- ---------- ---------- ---------- ----------  ----------
total        2      1.30       1.44          0       2166      75736       71825

See Also:

- Oracle Database Advanced Application Developer's Guide for an overview of bulk SQL

- Oracle Database Advanced Application Developer's Guide for more specific information about when to use bulk SQL

- Oracle Database PL/SQL Language Reference for more information about bulk SQL

About Concurrency and Scalability

The better your application handles concurrency, the more scalable it is.

Concurrency is the simultaneous execution of multiple transactions. Statements within concurrent transactions can update the same data. Concurrent transactions must produce meaningful and consistent results. Therefore, a multiuser database must provide the following:

- Data concurrency , which ensures that users can access data at the same time.

- Data consistency, which ensures that each user sees a consistent view of the data, including visible changes from his or her own transactions and committed transactions of other users

Oracle Database Express Edition maintains data consistency by using a multiversion consistency model and various types of locks and transaction isolation levels. For an overview of the Oracle Database Express Edition locking mechanism, see Oracle Database Concepts. For an overview of Oracle Database Express Edition transaction isolation levels, see Oracle Database Concepts.

To describe consistent transaction behavior when transactions run concurrently, database researchers have defined a transaction isolation category called serializable. A serializable transaction operates in an environment that appears to be a single-user database. Serializable transactions are desirable in specific cases, but for 99% of the work load, read committed isolation is perfect.

Oracle Database Express Edition has features that improve concurrency and scalability—for example, sequences, latches, nonblocking reads and writes, and shared SQL.

This section contains:

- About Sequences and Concurrency

- About Latches and Concurrency

- About Nonblocking Reads and Writes and Concurrency

- About Shared SQL and Concurrency

See Also:
Oracle Database Concepts for more information about data concurrency and consistency

About Sequences and Concurrency

A sequence is a schema object from which multiple users can generate unique integers, which is very useful when you need unique primary keys.

Without sequences, unique primary key values must be produced programmatically. A user gets a new primary key value by selecting the most recently produced value and incrementing it. This technique requires a lock during the transaction and causes multiple users to wait for the next primary key value—that is, the transactions serialize. Sequences eliminate serialization, thereby improving the concurrency and scalability of your application.

See Also:

- Oracle Database Concepts for information about concurrent access to sequences

- "Creating and Managing Sequences"

About Latches and Concurrency

A latch is a simple, low-level serialization mechanism that coordinates multiuser access to shared data structures. Latches protect shared memory resources from corruption when accessed by multiple processes.

An increase in latches means more concurrency-based waits, and therefore a decrease in scalability. If you can use either an approach that runs slightly faster during development or one that uses fewer latches, use the latter.

See Also:

- Oracle Database Concepts for information about latches

- Oracle Database Concepts for information about mutexes, which are like latches for single objects

About Nonblocking Reads and Writes and Concurrency

In Oracle Database Express Edition, nonblocking reads and writes let queries execute concurrently with changes to the data they are reading, without blocking or stopping. Nonblocking reads and writes let one session read data while another session is changing that data.

About Shared SQL and Concurrency

Oracle Database Express Edition compiles a SQL statement into an executable object once, and then other sessions can reuse the object for as long as it exists. This Oracle Database Express Edition feature, called shared SQL, lets the database do very resource-intensive operations—compiling and optimizing SQL statements—only once, instead of every time a session uses the same SQL statement.

See Also:
Oracle Database Concepts for more information about shared SQL

Limiting the Number of Concurrent Sessions

The more concurrent sessions you have, the more concurrency-based waits you have, and the slower your response time is.

If your computer has n CPU cores, then at most n sessions can really be concurrently active. Each additional "concurrent" session must wait for a CPU core to be available before it can become active. If some waiting sessions are waiting only for I/O, then increasing the number of concurrent sessions to slightly more than n might slightly improve runtime performance. However, increasing the number of concurrent sessions too much will significantly reduce runtime performance.

The SESSIONS initialization parameter determines the maximum number of concurrent users in the system. For details, see Oracle Database Reference.

See Also:
http://www.youtube.com/watch?v=xNDnVOCdvQ0 for a video that shows the effect of reducing the number of concurrent sessions on a computer with 12 CPU cores from thousands to 96

Comparing Programming Techniques with Runstats

This section contains:

- About Runstats

- Setting Up Runstats

- Using Runstats

About Runstats

The Runstats tool lets you compare the performance of two programming techniques to see which is better.

Runstats measures:

- Elapsed time for each technique in hundredths of seconds (hsec)

- Elapsed time for the first technique as a percentage of that of the second technique

- System statistics for the two techniques (for example, parse calls)

- Latching for the two techniques

Of the preceding measurements, the most important is latching (see "About Latches and Concurrency").

See Also:
Example 8-1, which uses Runstats

Setting Up Runstats

This section shows how set up the Runstats tool, which is implemented as a package that uses a view and a temporary table.

Note:
For step 1 of the following procedure, you need the SELECT privilege on the dynamic performance views V$STATNAME, V$MYSTAT, and V$LATCH. If you cannot get this privilege, then have someone who has the privilege create the view in step 1 and grant you the SELECT privilege on it.

To set up the Runstats tool:

1. Create the view that Runstats uses:

CREATE OR REPLACE VIEW stats
AS SELECT 'STAT...' || a.name name, b.value
FROM V$STATNAME a, V$MYSTAT b
WHERE a.statistic# = b.statistic#
UNION ALL
SELECT 'LATCH.' || name, gets
FROM V$LATCH;

2. Create the temporary table that Runstats uses:

DROP TABLE run_stats;

CREATE GLOBAL TEMPORARY TABLE run_stats
( runid VARCHAR2(15),
name VARCHAR2(80),
value INT )
ON COMMIT PRESERVE ROWS;

3. Create this package specification:

CREATE OR REPLACE PACKAGE runstats_pkg
AS
PROCEDURE rs_start;
PROCEDURE rs_middle;
PROCEDURE rs_stop( p_difference_threshold IN NUMBER DEFAULT 0 );
end;
/

The parameter p_difference_threshold controls the amount of statistics and latching data that Runstats displays. Runstats displays data only when the difference for the two techniques is greater than p_difference_threshold. By default, Runstats displays all data.

4. Create this package body:

CREATE OR REPLACE PACKAGE BODY runstats_pkg
AS
g_start NUMBER;
g_run1 NUMBER;
g_run2 NUMBER;

PROCEDURE rs_start
IS
BEGIN
DELETE FROM run_stats;

INSERT INTO run_stats
SELECT 'before', stats.* FROM stats;

g_start := DBMS_UTILITY.GET_TIME;
END rs_start;

PROCEDURE rs_middle
IS
BEGIN
g_run1 := (DBMS_UTILITY.GET_TIME - g_start);

INSERT INTO run_stats
SELECT 'after 1', stats.* FROM stats;

g_start := DBMS_UTILITY.GET_TIME;
END rs_middle;

PROCEDURE rs_stop( p_difference_threshold IN NUMBER DEFAULT 0 )
IS
BEGIN
g_run2 := (DBMS_UTILITY.GET_TIME - g_start);

DBMS_OUTPUT.PUT_LINE
('Run 1 ran in ' || g_run1 || ' hsec');

DBMS_OUTPUT.PUT_LINE
('Run 2 ran in ' || g_run2 || ' hsec');

DBMS_OUTPUT.PUT_LINE
('Run 1 ran in ' || round(g_run1/g_run2*100, 2) || '% of the time of run 2');

DBMS_OUTPUT.PUT_LINE( CHR(9) );

INSERT INTO run_stats
SELECT 'after 2', stats.* FROM stats;

DBMS_OUTPUT.PUT_LINE
( RPAD( 'Name', 30 ) ||
LPAD( 'Run 1', 14) ||
LPAD( 'Run 2', 14) ||
LPAD( 'Difference', 14)
);

FOR x IN
( SELECT RPAD( a.name, 30 ) ||
TO_CHAR( b.value - a.value, '9,999,999,999' ) ||
TO_CHAR( c.value - b.value, '9,999,999,999' ) ||
TO_CHAR( ( (c.value - b.value) - (b.value - a.value)),
'9,999,999,999' ) data
FROM run_stats a, run_stats b, run_stats c
WHERE a.name = b.name
AND b.name = c.name
AND a.runid = 'before'
AND b.runid = 'after 1'
AND c.runid = 'after 2'
AND (c.value - a.value) > 0
AND abs((c.value - b.value) - (b.value - a.value)) >
p_difference_threshold
ORDER BY ABS((c.value - b.value) - (b.value - a.value))
) LOOP
DBMS_OUTPUT.PUT_LINE( x.data );
END LOOP;

DBMS_OUTPUT.PUT_LINE( CHR(9) );

DBMS_OUTPUT.PUT_LINE(
'Run 1 latches total compared to run 2 -- difference and percentage' );

DBMS_OUTPUT.PUT_LINE
( LPAD( 'Run 1', 14) ||
LPAD( 'Run 2', 14) ||
LPAD( 'Diff', 14) ||
LPAD( 'Pct', 10)
);

FOR x IN
( SELECT TO_CHAR( run1, '9,999,999,999' ) ||
TO_CHAR( run2, '9,999,999,999' ) ||
TO_CHAR( diff, '9,999,999,999' ) ||
TO_CHAR( ROUND( g_run1/g_run2*100, 2), '99,999.99' ) || '%' data
FROM ( SELECT SUM (b.value - a.value) run1,
SUM (c.value - b.value) run2,
SUM ( (c.value - b.value) - (b.value - a.value)) diff
FROM run_stats a, run_stats b, run_stats c
WHERE a.name = b.name
AND b.name = c.name
AND a.runid = 'before'
AND b.runid = 'after 1'
AND c.runid = 'after 2'
AND a.name like 'LATCH%'
)
) LOOP
DBMS_OUTPUT.PUT_LINE( x.data );
END LOOP;

END rs_stop;

END;
/

See Also:

- "Creating Views"

- "Creating Tables"

- "Tutorial: Creating a Package Specification"

- "Tutorial: Creating a Package Body"

- Oracle Database Reference for information about dynamic performance views

Using Runstats

To use Runstats to compare two programming techniques, invoke the runstats_pkg procedures from an anonymous block, using this syntax:

[ DECLARE local_declarations ]
BEGIN
runstats_pkg.rs_start;
code_for_first_technique
runstats_pkg.rs_middle;
code_for_second_technique
runstats_pkg.rs_stop(n);
END;
/

See Also:
Example 8-1, which uses Runstats

Recommended Programming Practices

This section contains:

- Use Instrumentation Packages

- Statistics Gathering and Application Tracing

- Use Existing Functionality

- Cover Database Tables with Editioning Views

Use Instrumentation Packages

Oracle Database Express Edition supplies instrumentation packages whose subprograms let your application generate trace information whenever necessary. Using this trace information, you can debug your application without a debugger and identify code that performs badly. Instrumentation provides your application with considerable functionality; therefore, it is not overhead. Overhead is something that you can remove without losing much benefit.

Some instrumentation packages that Oracle Database Express Edition supplies are:

- DBMS_APPLICATION_INFO, which enables a system administrator to track the performance of your application by module.
For more information about DBMS_APPLICATION_INFO, see Oracle Database PL/SQL Packages and Types Reference.

- DBMS_SESSION, which enables your application to access session information and set preferences and security levels
For more information about DBMS_SESSION, see Oracle Database PL/SQL Packages and Types Reference.

- UTL_FILE, which enables your application to read and write operating system text files
For more information about UTL_FILE, see Oracle Database PL/SQL Packages and Types Reference.

See Also:
Oracle Database PL/SQL Packages and Types Reference for a summary of PL/SQL packages that Oracle Database Express Edition supplies

Statistics Gathering and Application Tracing

Database statistics provide information about the type of load on the database and the internal and external resources used by the database. To accurately diagnose performance problems with the database using ADDM, statistics must be available. For information about statistics gathering, see Oracle Database 2 Day + Performance Tuning Guide.

Note:
If Oracle Enterprise Manager is unavailable, then you can gather statistics using DBMS_MONITOR subprograms, described in Oracle Database PL/SQL Packages and Types Reference.

Oracle Database Express Edition provides several tracing tools that can help you monitor and analyze Oracle Database Express Edition applications. For details, see Oracle Database SQL Tuning Guide.

Use Existing Functionality

When developing your application, use the existing functionality of your programming language, your operating system, Oracle Database Express Edition, and the PL/SQL packages and types that Oracle Database Express Edition supplies as much as possible. An application that uses existing functionality is easier to develop and maintain than one that does not, and it also runs faster.

Examples of existing functionality that many developers reinvent are:

- Constraints
For introductory information about constraints, see "Ensuring Data Integrity in Tables."

- SQL functions (functions that are "built into" SQL)
For information about SQL functions, see Oracle Database SQL Language Reference.

- Sequences (which can generate unique sequential values)
See "Creating and Managing Sequences".

- Auditing (the monitoring and recording of selected user database actions)
For introductory information about auditing, see Oracle Database 2 Day + Security Guide.

- Replication (the process of copying and maintaining database objects, such as tables, in multiple databases that comprise a distributed database system)
For an overview of replication, see Oracle Database Advanced Replication.

- Message queuing (how web-based business applications communicate with each other)
For introductory information about Oracle Database Advanced Queuing (AQ), see Oracle Database Advanced Queuing User's Guide.

- Maintaining a history of record changes
For introductory information about Workspace Manager, see Oracle Database Workspace Manager Developer's Guide.

In Example 8-4, two concurrent transactions dequeue messages stored in a table (that is, each transaction finds and locks the next unprocessed row of the table). Rather than simply invoking the DBMS_AQ.DEQUEUE procedure (described in Oracle Database PL/SQL Packages and Types Reference), the example creates a function-based index on the table and then uses that function in each transaction to retrieve the rows and display the messages.

Example 8-4 Concurrent Dequeuing Transactions

Create table:

DROP TABLE t;
CREATE TABLE t
( id             NUMBER PRIMARY KEY,
processed_flag VARCHAR2(1),
payload        VARCHAR2(20)
);

Create index on table:

CREATE INDEX t_idx ON
t( DECODE( processed_flag, 'N', 'N' ) );

Populate table:

INSERT INTO t
SELECT r,
CASE WHEN MOD(r,2) = 0 THEN 'N' ELSE 'Y' END,
'payload ' || r
FROM (SELECT LEVEL r FROM DUAL CONNECT BY LEVEL <= 5);

Show table:

SELECT * FROM t;

Result:

ID P PAYLOAD
---------- - --------------------
1 Y payload 1
2 N payload 2
3 Y payload 3
4 N payload 4
5 Y payload 5

5 rows selected.

First transaction:

DECLARE
l_rec t%ROWTYPE;
CURSOR c IS
SELECT *
FROM t
WHERE DECODE(processed_flag,'N','N') = 'N'
FOR UPDATE
SKIP LOCKED;
BEGIN
OPEN c;

FETCH c INTO l_rec;

IF ( c%FOUND ) THEN
DBMS_OUTPUT.PUT_LINE( 'Got row ' || l_rec.id || ', ' || l_rec.payload );
END IF;

CLOSE c;
END;
/

Result:

Got row 2, payload 2

Concurrent transaction:

DECLARE
PRAGMA AUTONOMOUS_TRANSACTION;
l_rec t%ROWTYPE;
CURSOR c IS
SELECT *
FROM t
WHERE DECODE(processed_flag,'N','N') = 'N'
FOR UPDATE
SKIP LOCKED;
BEGIN
OPEN c;

FETCH c INTO l_rec;

IF ( c%FOUND ) THEN
DBMS_OUTPUT.PUT_LINE( 'Got row ' || l_rec.id || ', ' || l_rec.payload );
END IF;

CLOSE c;
COMMIT;
END;
/

Result:

Got row 4, payload 4

The code in Example 8-4 implements a feature similar to a DBMS_AQ.DEQUEUE invocation but with fewer capabilities. The development time saved by using existing functionality (in this case, function-based indexes) can be large.

See Also:

- Oracle Database PL/SQL Packages and Types Reference

- Oracle Database New Features Guide (with each release)

- Oracle Database Concepts (with each release)

Cover Database Tables with Editioning Views

If your application uses database tables, then cover each one with an editioning view so that you can use edition-based redefinition (EBR) to upgrade the database component of your application while it is in use, thereby minimizing or eliminating down time. For information about EBR, see Oracle Database Advanced Application Developer's Guide. For information about editioning views, see Oracle Database Advanced Application Developer's Guide.

Recommended Security Practices

When granting privileges on the schema objects that comprise your application, use the principle of least privilege. That is, give users only the privileges that they need. For more information about the principle of least privilege, see Oracle Database 2 Day + Security Guide.

See Also:
"Using Bind Arguments to Improve Scalability" for information about using bind arguments instead of string literals, which is the most effective way to make your code invulnerable to SQL injection attacks

9 Developing a Simple Oracle Database Express Edition Application

This chapter shows how to develop a simple Oracle Database Express Edition application.

This chapter contains:

- About the Application

- Creating the Schemas for the Application

- Granting Privileges to the Schemas

- Creating the Schema Objects and Loading the Data

- Creating the employees_pkg Package

- Creating the admin_pkg Package

About the Application

This section contains:

- Purpose of the Application

- Structure of the Application

- Naming Conventions in the Application

Purpose of the Application

The application is intended for two kinds of users in a company:

- Typical users (managers of employees)

- Application administrators

Typical users can do the following:

- Get the employees in a given department

- Get the job history for a given employee

- Show general information for a given employee (name, department, job, manager, salary, and so on)

- Change the salary of a given employee

- Change the job of a given employee

Application administrators can do the following:

- Change the ID, title, or salary range of an existing job

- Add a new job

- Change the ID, name, or manager of an existing department

- Add a new department

Structure of the Application

This section contains:

- Schema Objects of the Application

- Schemas for the Application

Schema Objects of the Application

The application is composed of these schema objects:

- Four tables, which store data about:

- Jobs

- Departments

- Employees

- Job history of employees

- Four editioning views, which cover the tables, enabling you to use edition-based redefinition (EBR) to upgrade the finished application when it is in use

- Two triggers, which enforce business rules

- Two sequences that generate unique primary keys for new departments and new employees

- Two packages:

- employees_pkg, the application program interface (API) for typical users

- admin_pkg, the API for application administrators

The typical users and application administrators access the application only through its APIs. Therefore, they can change the data only by invoking package subprograms.

See Also:

- "About Oracle Database Express Edition" for information about schema objects

- Oracle Database Advanced Application Developer's Guide for information about EBR

Schemas for the Application

For security, the application uses these five schemas (or users), each of which has only the privileges that it needs:

- app_data, who owns all the schema objects except the packages and loads its tables with data from tables in the sample schema HR
The developers who create the packages never work in this schema. Therefore, they cannot accidently alter or drop application schema objects.

- app_code, who owns only the package employees_pkg
The developers of employees_pkg work in this schema.

- app_admin, who owns only the package admin_pkg
The developers of admin_pkg work in this schema.

- app_user, the typical application user, who owns nothing and can only execute employees_pkg
The middle-tier application server connects to the database in the connection pool as app_user. If this schema is compromised—by a SQL injection bug, for example—the attacker can see and change only what employees_pkg subprograms let it see and change. The attacker cannot drop tables, escalate privileges, create or alter schema objects, or anything else.

- app_admin_user, an application administrator, who owns nothing and can only execute admin_pkg and employees_pkg
The connection pool for this schema is very small, and only privileged users can access it. If this schema is compromised, the attacker can see and change only what admin_pkg and employees_pkg subprograms let it see and change.

Suppose that instead of app_user and app_admin_user, the application had only one schema that owned nothing and could execute both employees_pkg and admin_pkg. The connection pool for this schema would have to be large enough for both the typical users and the application administrators. If there were a SQL injection bug in employees_pkg, a typical user who exploited that bug could access admin_pkg.

Suppose that instead of app_data, app_code, and app_admin, the application had only one schema that owned all the schema objects, including the packages. The packages would then have all privileges on the tables, which would be both unnecessary and undesirable.

For example, suppose that you have an audit trail table, AUDIT_TRAIL. You want the developers of employees_pkg to be able to write to AUDIT_TRAIL, but not read or change it. You want the developers of admin_pkg to be able to read AUDIT_TRAIL and write to it, but not change it. If AUDIT_TRAIL, employees_pkg, and admin_pkg belong to the same schema, then the developers of the two packages have all privileges on AUDIT_TRAIL. However, if AUDIT_TRAIL belongs to app_data, employees_pkg belongs to app_code, and admin_pkg belongs to app_admin, then you can connect to the database as app_data and do this:

GRANT INSERT ON AUDIT_TRAIL TO app_code;
GRANT INSERT, SELECT ON AUDIT_TRAIL TO app_admin;

See Also:

- "About Oracle Database Express Edition" for information about schemas

- "About Sample Schema HR" for information about sample schema HR

- "Recommended Security Practices"

Naming Conventions in the Application

The application uses these naming conventions:

Item

Name

Table

table#

Editioning view for table#

table

Trigger on editioning view table

table_{a|b}event[_fer] where:

- a identifies an AFTER trigger.

- b identifies a BEFORE trigger.

- fer identifies a FOR EACH ROW trigger.

- event identifies the event that fires the trigger. For example: i for INSERT, iu for INSERT or UPDATE, d for DELETE.

PRIMARY KEY constraint in table#

table_pk

NOT NULL constraint on table#.column

table_column_not_nullFoot 1

UNIQUE constraint on table#.column

table_column_uniqueFootref 1

CHECK constraint on table#.column

table_column_checkFootref 1

REF constraint on table1#.column to table2#.column

table1_to_table2_fkFootref 1

REF constraint on table1#.column1 to table2#.column2

table1_col1_to_table2_col2_fkFootref 1 Foot 2

Sequence for table#

table_sequence

Parameter name

p_name

Local variable name

l_name

Footnote 1 table, table1, and table2 are abbreviated to emp for employees, dept for departments, and job_hist for job_history.

Footnote 2 col1 and col2 are abbreviations of column names column1 and column2. A constraint name cannot have more than 30 characters.

Creating the Schemas for the Application

Using the procedure in this section, create the schemas for the application, whose names are:

- app_data

- app_code

- app_admin

- app_user

- app_admin_user

Note:
For the following procedure, you need the name and password of a user who has the CREATE USER and DROP USER system privileges.

To create the schema (or user) schema_name:

1. Using SQL*Plus, connect to Oracle Database Express Edition as a user with the CREATE USER and DROP USER system privileges.
The SQL> prompt appears.

2. In case the schema exists, drop the schema and its objects with this SQL statement:

DROP USER schema_name CASCADE;

If the schema existed, the system responds:

User dropped.

If the schema did not exist, the system responds:

DROP USER schema_name CASCADE
*
ERROR at line 1:
ORA-01918: user 'schema_name' does not exist

3. If schema_name is either app_data, app_code, or app_admin, then create the schema with this SQL statement:

CREATE USER schema_name IDENTIFIED BY password
DEFAULT TABLESPACE USERS
QUOTA UNLIMITED ON USERS
ENABLE EDITIONS;

Otherwise, create the schema with this SQL statement:

CREATE USER schema_name IDENTIFIED BY password
ENABLE EDITIONS;

Caution:
Choose a secure password. For guidelines for secure passwords, see Oracle Database Security Guide.

The system responds:

User created.

4. (Optional) In SQL Developer, create a connection for the schema, using the instructions in "Connecting to Oracle Database Express Edition from SQL Developer".

See Also:

- "About the Application"

- "Connecting to Oracle Database Express Edition from SQL*Plus"

- Oracle Database SQL Language Reference for information about the DROP USER statement

- Oracle Database SQL Language Reference for information about the CREATE USER statement

Granting Privileges to the Schemas

To grant privileges to schemas, use the SQL statement GRANT. You can enter the GRANT statements either in SQL*Plus or in the Worksheet of SQL Developer. For security, grant each schema only the privileges that it needs.

This section contains:

- Granting Privileges to the app_data Schema

- Granting Privileges to the app_code Schema

- Granting Privileges to the app_admin Schema

- Granting Privileges to the app_user and app_admin_user Schemas

See Also:

- "About the Application"

- Oracle Database SQL Language Reference for information about the GRANT statement

Granting Privileges to the app_data Schema

Grant to the app_data schema only the privileges to do the following:

- Connect to Oracle Database Express Edition:

GRANT CREATE SESSION TO app_data;

- Create the tables, views, triggers, and sequences for the application:

GRANT CREATE TABLE, CREATE VIEW, CREATE TRIGGER, CREATE SEQUENCE TO app_data;

- Load data from four tables in the sample schema HR into its own tables:

GRANT SELECT ON HR.DEPARTMENTS TO app_data;
GRANT SELECT ON HR.EMPLOYEES TO app_data;
GRANT SELECT ON HR.JOB_HISTORY TO app_data;
GRANT SELECT ON HR.JOBS TO app_data;

Granting Privileges to the app_code Schema

Grant to the app_code schema only the privileges to do the following:

- Connect to Oracle Database Express Edition:

GRANT CREATE SESSION TO app_code;

- Create the package employees_pkg:

GRANT CREATE PROCEDURE TO app_code;

- Create synonyms (for convenience):

GRANT CREATE SYNONYMS TO app_code;

Granting Privileges to the app_admin Schema

Grant to the app_admin schema only the privileges to do the following:

- Connect to Oracle Database Express Edition:

GRANT CREATE SESSION TO app_admin;

- Create the package admin_pkg:

GRANT CREATE PROCEDURE TO app_admin;

- Create synonyms (for convenience):

GRANT CREATE SYNONYMS TO app_admin;

Granting Privileges to the app_user and app_admin_user Schemas

Grant to the app_user and app_admin_user schemas only the privileges to do the following:

- Connect to Oracle Database Express Edition:

GRANT CREATE SESSION TO app_user;
GRANT CREATE SESSION TO app_admin_user;

- Create synonyms (for convenience):

GRANT CREATE SYNONYMS TO app_user;
GRANT CREATE SYNONYMS TO app_admin_user;

Creating the Schema Objects and Loading the Data

This section shows how to create the tables, editioning views, triggers, and sequences for the application, how to load data into the tables, and how to grant privileges on these schema objects to the users that need them.

To create the schema objects and load the data:

1. Connect to Oracle Database Express Edition as user app_data.
For instructions, see either "Connecting to Oracle Database Express Edition from SQL*Plus" or "Connecting to Oracle Database Express Edition from SQL Developer".

2. Create the tables, with all necessary constraints except the foreign key constraint that you must add after you load the data.

3. Create the editioning views.

4. Create the triggers.

5. Create the sequences.

6. Load the data into the tables.

7. Add the foreign key constraint.

This section contains:

- Creating the Tables

- Creating the Editioning Views

- Creating the Triggers

- Creating the Sequences

- Loading the Data

- Adding the Foreign Key Constraint

- Granting Privileges on the Schema Objects to Users

Creating the Tables

Note:
You must be connected to Oracle Database Express Edition as user app_data.

This section shows how to create the tables for the application, with all necessary constraints except one, which you must add after you load the data.

In the following procedure, you can enter the statements either in SQL*Plus or in the Worksheet of SQL Developer. Alternatively, you can create the tables with the SQL Developer tool Create Table.

To create the tables:

1. Create jobs#, which stores information about the jobs in the company (one row for each job):

CREATE TABLE jobs#
( job_id      VARCHAR2(10)
CONSTRAINT jobs_pk PRIMARY KEY,
job_title   VARCHAR2(35)
CONSTRAINT jobs_job_title_not_null NOT NULL,
min_salary  NUMBER(6)
CONSTRAINT jobs_min_salary_not_null NOT NULL,
max_salary  NUMBER(6)
CONSTRAINT jobs_max_salary_not_null NOT NULL
)
/

2. Create departments#, which stores information about the departments in the company (one row for each department):

CREATE TABLE departments#
( department_id    NUMBER(4)
CONSTRAINT departments_pk PRIMARY KEY,
department_name  VARCHAR2(30)
CONSTRAINT department_name_not_null NOT NULL
CONSTRAINT department_name_unique UNIQUE,
manager_id       NUMBER(6)
)
/

3. Create employees#, which stores information about the employees in the company (one row for each employee):

CREATE TABLE employees#
( employee_id     NUMBER(6)
CONSTRAINT employees_pk PRIMARY KEY,
first_name      VARCHAR2(20)
CONSTRAINT emp_first_name_not_null NOT NULL,
last_name       VARCHAR2(25)
CONSTRAINT emp_last_name_not_null NOT NULL,
email_addr      VARCHAR2(25)
CONSTRAINT emp_email_addr_not_null NOT NULL,
hire_date       DATE
DEFAULT TRUNC(SYSDATE)
CONSTRAINT emp_hire_date_not_null NOT NULL
CONSTRAINT emp_hire_date_check
CHECK(TRUNC(hire_date) = hire_date),
country_code    VARCHAR2(5)
CONSTRAINT emp_country_code_not_null NOT NULL,
phone_number    VARCHAR2(20)
CONSTRAINT emp_phone_number_not_null NOT NULL,
job_id          CONSTRAINT emp_job_id_not_null NOT NULL
CONSTRAINT emp_jobs_fk REFERENCES jobs#,
job_start_date  DATE
CONSTRAINT emp_job_start_date_not_null NOT NULL,
CONSTRAINT emp_job_start_date_check
CHECK(TRUNC(JOB_START_DATE) = job_start_date),
salary          NUMBER(6)
CONSTRAINT emp_salary_not_null NOT NULL,
manager_id      CONSTRAINT emp_mgr_to_empno_fk REFERENCES employees#,
department_id   CONSTRAINT emp_to_dept_fk REFERENCES departments#
)
/

The reasons for the REF constraints are:

- An employee must have an existing job. That is, values in the column employees#.job_id must also be values in the column jobs#.job_id.

- An employee must have a manager who is also an employee. That is, values in the column employees#.manager_id must also be values in the column employees#.employee_id.

- An employee must work in an existing department. That is, values in the column employees#.department_id must also be values in the column departments#.department_id.

Also, the manager of an employee must be the manager of the department in which the employee works. That is, values in the column employees#.manager_id must also be values in the column departments#.manager_id. However, you could not specify the necessary constraint when you created departments#, because employees# did not exist yet. Therefore, you must add a foreign key constraint to departments# later (see "Adding the Foreign Key Constraint").

4. Create job_history#, which stores the job history of each employee in the company (one row for each job held by the employee):

CREATE TABLE job_history#
( employee_id  CONSTRAINT job_hist_to_employees_fk REFERENCES employees#,
job_id       CONSTRAINT job_hist_to_jobs_fk REFERENCES jobs#,
start_date   DATE
CONSTRAINT job_hist_start_date_not_null NOT NULL,
end_date     DATE
CONSTRAINT job_hist_end_date_not_null NOT NULL,
department_id
CONSTRAINT job_hist_to_departments_fk REFERENCES departments#
CONSTRAINT job_hist_dept_id_not_null NOT NULL,
CONSTRAINT job_history_pk PRIMARY KEY(employee_id,start_date),
CONSTRAINT job_history_date_check CHECK( start_date < end_date )
)
/

The reasons for the REF constraints are that the employee, job, and department must exist. That is:

- Values in the column job_history#.employee_id must also be values in the column employees#.employee_id.

- Values in the column job_history#.job_id must also be values in the column jobs#.job_id.

- Values in the column job_history#.department_id must also be values in the column departments#.department_id.

See Also:
"Creating Tables"

Creating the Editioning Views

Note:
You must be connected to Oracle Database Express Edition as user app_data.

To create the editioning views, use the following statements (in any order). You can enter the statements either in SQL*Plus or in the Worksheet of SQL Developer. Alternatively, you can create the tables with the SQL Developer tool Create View.

CREATE EDITIONING VIEW jobs AS SELECT * FROM jobs#
/
CREATE EDITIONING VIEW departments AS SELECT * FROM departments#
/
CREATE EDITIONING VIEW employees AS SELECT * FROM employees#
/
CREATE EDITIONING VIEW job_history AS SELECT * FROM job_history#
/

Note:
The application must always reference the base tables through the editioning views. Otherwise, the editioning views do not cover the tables and you cannot use EBR to upgrade the finished application when it is in use.

See Also:

- "Creating Views"

- Oracle Database Advanced Application Developer's Guide for general information about editioning views

- Oracle Database Advanced Application Developer's Guide for information about preparing an application to use editioning views

Creating the Triggers

Note:
You must be connected to Oracle Database Express Edition as user app_data.

The triggers in the application enforce these business rules:

- An employee with job j must have a salary between the minimum and maximum salaries for job j.

- If an employee with job j has salary s, then you cannot change the minimum salary for j to a value greater than s or the maximum salary for j to a value less than s. (To do so would make existing data invalid.)

This section contains:

- Creating the Trigger to Enforce the First Business Rule

- Creating the Trigger to Enforce the Second Business Rule

See Also:
Chapter 6, "Using Triggers," for information about triggers

Creating the Trigger to Enforce the First Business Rule

The first business rule is: An employee with job j must have a salary between the minimum and maximum salaries for job j.

This rule could be violated either when a new row is inserted into the employees table or when the salary or job_id column of the employees table is updated.

To enforce the rule, create the following trigger on the editioning view employees. You can enter the CREATE TRIGGER statement either in SQL*Plus or in the Worksheet of SQL Developer. Alternatively, you can create the trigger with the SQL Developer tool Create Trigger.

CREATE OR REPLACE TRIGGER employees_aiufer
AFTER INSERT OR UPDATE OF salary, job_id ON employees FOR EACH ROW
DECLARE
l_cnt NUMBER;
BEGIN
LOCK TABLE jobs IN SHARE MODE;  -- Ensure that jobs does not change
-- during the following query.
SELECT COUNT(*) INTO l_cnt
FROM jobs
WHERE job_id = :NEW.job_id
AND :NEW.salary BETWEEN min_salary AND max_salary;

IF (l_cnt<>1) THEN
RAISE_APPLICATION_ERROR( -20002,
CASE
WHEN :new.job_id = :old.job_id
THEN 'Salary modification invalid'
ELSE 'Job reassignment puts salary out of range'
END );
END IF;
END;
/

LOCK TABLE jobs IN SHARE MODE prevents other users from changing the table jobs while the trigger is querying it. Preventing changes to jobs during the query is necessary because nonblocking reads prevent the trigger from "seeing" changes that other users make to jobs while the trigger is changing employees (and prevent those users from "seeing" the changes that the trigger makes to employees).

Another way to prevent changes to jobs during the query is to include the FOR UPDATE clause in the SELECT statement. However, SELECT FOR UPDATE restricts concurrency more than LOCK TABLE IN SHARE MODE does.

LOCK TABLE jobs IN SHARE MODE prevents other users from changing jobs, but not from locking jobs in share mode themselves. Changes to jobs will probably be much rarer than changes to employees. Therefore, locking jobs in share mode provides more concurrency than locking a single row of jobs in exclusive mode.

See Also:

- Oracle Database Advanced Application Developer's Guide for information about locking tables IN SHARE MODE

- Oracle Database PL/SQL Language Reference for information about SELECT FOR UPDATE

- "Creating Triggers"

- "Tutorial: Showing How the employees_pkg Subprograms Work" to see how the employees_aiufer trigger works

Creating the Trigger to Enforce the Second Business Rule

The second business rule is: If an employee with job j has salary s, then you cannot change the minimum salary for j to a value greater than s or the maximum salary for j to a value less than s. (To do so would make existing data invalid.)

This rule could be violated when the min_salary or max_salary column of the jobs table is updated.

To enforce the rule, create the following trigger on the editioning view jobs. You can enter the CREATE TRIGGER statement either in SQL*Plus or in the Worksheet of SQL Developer. Alternatively, you can create the trigger with the SQL Developer tool Create Trigger.

CREATE OR REPLACE TRIGGER jobs_aufer
AFTER UPDATE OF min_salary, max_salary ON jobs FOR EACH ROW
WHEN (NEW.min_salary > OLD.min_salary OR NEW.max_salary < OLD.max_salary)
DECLARE
l_cnt NUMBER;
BEGIN
LOCK TABLE employees IN SHARE MODE;

SELECT COUNT(*) INTO l_cnt
FROM employees
WHERE job_id = :NEW.job_id
AND salary NOT BETWEEN :NEW.min_salary and :NEW.max_salary;

IF (l_cnt>0) THEN
RAISE_APPLICATION_ERROR( -20001,
'Salary update would violate ' || l_cnt || ' existing employee records' );
END IF;
END;
/

LOCK TABLE employees IN SHARE MODE prevents other users from changing the table employees while the trigger is querying it. Preventing changes to employees during the query is necessary because nonblocking reads prevent the trigger from "seeing" changes that other users make to employees while the trigger is changing jobs (and prevent those users from "seeing" the changes that the trigger makes to jobs).

For this trigger, SELECT FOR UPDATE is not an alternative to LOCK TABLE IN SHARE MODE. While you are trying to change the salary range for this job, this trigger must prevent other users from changing a salary to be outside the new range. Therefore, the trigger must lock all rows in the employees table that have this job_id and lock all rows that someone could update to have this job_id.

One alternative to LOCK TABLE employees IN SHARE MODE is to use the DBMS_LOCK package to create a named lock with the name of the job_id and then use triggers on both the employees and jobs tables to use this named lock to prevent concurrent updates. However, using DBMS_LOCK and multiple triggers negatively impacts runtime performance.

Another alternative to LOCK TABLE employees IN SHARE MODE is to create a trigger on the employees table which, for each changed row of employees, locks the corresponding job row in jobs. However, this approach causes excessive work on updates to the employees table, which are frequent.

LOCK TABLE employees IN SHARE MODE is simpler than the preceding alternatives, and changes to the jobs table are rare and likely to happen at application maintenance time, when locking the table does not inconvenience users.

See Also:

- Oracle Database Advanced Application Developer's Guide for information about locking tables with SHARE MODE

- Oracle Database PL/SQL Packages and Types Reference for information about the DBMS_LOCK package

- "Creating Triggers"

- "Tutorial: Showing How the admin_pkg Subprograms Work"

Creating the Sequences

Note:
You must be connected to Oracle Database Express Edition as user app_data.

To create the sequences that generate unique primary keys for new departments and new employees, use the following statements (in either order). You can enter the statements either in SQL*Plus or in the Worksheet of SQL Developer. Alternatively, you can create the sequences with the SQL Developer tool Create Sequence.

CREATE SEQUENCE employees_sequence START WITH 210;
CREATE SEQUENCE departments_sequence START WITH 275;

To avoid conflict with the data that you will load from tables in the sample schema HR, the starting numbers for employees_sequence and departments_sequence must exceed the maximum values of employees.employee_id and departments.department_id, respectively. After "Loading the Data", this query displays these maximum values:

SELECT MAX(e.employee_id), MAX(d.department_id)
FROM employees e, departments d;

Result:

MAX(E.EMPLOYEE_ID) MAX(D.DEPARTMENT_ID)
------------------ --------------------
206                  270

See Also:
"Creating and Managing Sequences"

Loading the Data

Note:
You must be connected to Oracle Database Express Edition as user app_data.

Load the tables of the application with data from tables in the sample schema HR.

Note:
The following procedure references the tables of the application through their editioning views.

In the following procedure, you can enter the statements either in SQL*Plus or in the Worksheet of SQL Developer.

To load data into the tables:

1. Load jobs with data from the table HR.JOBS:

INSERT INTO jobs (job_id, job_title, min_salary, max_salary)
SELECT job_id, job_title, min_salary, max_salary
FROM HR.JOBS
/

Result:

19 rows created.

2. Load departments with data from the table HR.DEPARTMENTS:

INSERT INTO departments (department_id, department_name, manager_id)
SELECT department_id, department_name, manager_id
FROM HR.DEPARTMENTS
/

Result:

27 rows created.

3. Load employees with data from the tables HR.EMPLOYEES and HR.JOB_HISTORY, using searched CASE expressions and SQL functions to get employees.country_code and employees.phone_number from HR.phone_number and SQL functions and a scalar subquery to get employees.job_start_date from HR.JOB_HISTORY:

INSERT INTO employees (employee_id, first_name, last_name, email_addr,
hire_date, country_code, phone_number, job_id, job_start_date, salary,
manager_id, department_id)
SELECT employee_id, first_name, last_name, email, hire_date,
CASE WHEN phone_number LIKE '011.%'
THEN '+' || SUBSTR( phone_number, INSTR( phone_number, '.' )+1,
INSTR( phone_number, '.', 1, 2 ) -  INSTR( phone_number, '.' ) - 1 )
ELSE '+1'
END country_code,
CASE WHEN phone_number LIKE '011.%'
THEN SUBSTR( phone_number, INSTR(phone_number, '.', 1, 2 )+1 )
ELSE phone_number
END phone_number,
job_id,
NVL( (SELECT MAX(end_date+1)
FROM HR.JOB_HISTORY jh
WHERE jh.employee_id = employees.employee_id), hire_date),
salary, manager_id, department_id
FROM HR.EMPLOYEES
/

Result:

107 rows created.

Note:
The preceding INSERT statement fires the trigger created in "Creating the Trigger to Enforce the First Business Rule".

4. Load job_history with data from the table HR.JOB_HISTORY:

INSERT INTO job_history (employee_id, job_id, start_date, end_date,
department_id)
SELECT employee_id, job_id, start_date, end_date, department_id
FROM HR.JOB_HISTORY
/

Result:

10 rows created.

5. Commit the changes:

COMMIT;

See Also:

- "About the INSERT Statement"

- "About Sample Schema HR"

- "Using CASE Expressions in Queries"

- "Using NULL-Related Functions in Queries" for information about the NVL function

- Oracle Database SQL Language Reference for information about the SQL functions

Adding the Foreign Key Constraint

Note:
You must be connected to Oracle Database Express Edition as user app_data.

Now that the tables departments and employees contain data, add a foreign key constraint with the following ALTER TABLE statement. You can enter the statement either in SQL*Plus or in the Worksheet of SQL Developer. Alternatively, you can add the constraint with the SQL Developer tool Add Foreign Key.

ALTER TABLE departments#
ADD CONSTRAINT dept_to_emp_fk
FOREIGN KEY(manager_id) REFERENCES employees#;

If you add this foreign key constraint before departments# and employees# contain data, then you get this error when you try to load either of them with data:

ORA-02291: integrity constraint (APP_DATA.JOB_HIST_TO_DEPT_FK) violated - parent key not found

See Also:
"Tutorial: Adding Constraints to Existing Tables"

Granting Privileges on the Schema Objects to Users

Note:
You must be connected to Oracle Database Express Edition as user app_data.

To grant privileges to users, use the SQL statement GRANT. You can enter the GRANT statements either in SQL*Plus or in the Worksheet of SQL Developer.

Grant to app_code only the privileges that it needs to create employees_pkg:

GRANT SELECT, INSERT, UPDATE, DELETE ON employees TO app_code;
GRANT SELECT ON departments TO app_code;
GRANT SELECT ON jobs TO app_code;
GRANT SELECT, INSERT on job_history TO app_code;
GRANT SELECT ON employees_sequence TO app_code;

Grant to app_admin only the privileges that it needs to create admin_pkg:

GRANT SELECT, INSERT, UPDATE, DELETE ON jobs TO app_admin;
GRANT SELECT, INSERT, UPDATE, DELETE ON departments TO app_admin;
GRANT SELECT ON employees_sequence TO app_admin;
GRANT SELECT ON departments_sequence TO app_admin;

See Also:
Oracle Database SQL Language Reference for information about the GRANT statement

Creating the employees_pkg Package

This section shows how to create the employees_pkg package, how its subprograms work, how to grant the execute privilege on the package to the users who need it, and how those users can invoke one of its subprograms.

To create the employees_pkg package:

1. Connect to Oracle Database Express Edition as user app_code.
For instructions, see either "Connecting to Oracle Database Express Edition from SQL*Plus" or "Connecting to Oracle Database Express Edition from SQL Developer".

2. Create these synonyms:

CREATE SYNONYM employees FOR app_data.employees;
CREATE SYNONYM departments FOR app_data.departments;
CREATE SYNONYM jobs FOR app_data.jobs;
CREATE SYNONYM job_history FOR app_data.job_history;

You can enter the CREATE SYNONYM statements either in SQL*Plus or in the Worksheet of SQL Developer. Alternatively, you can create the tables with the SQL Developer tool Create Synonym.

3. Create the package specification.

4. Create the package body.

This section contains:

- Creating the Package Specification for employees_pkg

- Creating the Package Body for employees_pkg

- Tutorial: Showing How the employees_pkg Subprograms Work

- Granting the Execute Privilege to app_user and app_user_admin

- Tutorial: Invoking get_job_history as app_user or app_admin_user

See Also:

- "Creating Synonyms"

- "About Packages"

Creating the Package Specification for employees_pkg

Note:
You must be connected to Oracle Database Express Edition as user app_code.

To create the package specification for employees_pkg, the API for managers, use the following CREATE PACKAGE statement. You can enter the statement either in SQL*Plus or in the Worksheet of SQL Developer. Alternatively, you can create the package with the SQL Developer tool Create Package.

CREATE OR REPLACE PACKAGE employees_pkg
AS
PROCEDURE get_employees_in_dept
( p_deptno     IN     employees.department_id%TYPE,
p_result_set IN OUT SYS_REFCURSOR );

PROCEDURE get_job_history
( p_employee_id  IN     employees.department_id%TYPE,
p_result_set   IN OUT SYS_REFCURSOR );

PROCEDURE show_employee
( p_employee_id  IN     employees.employee_id%TYPE,
p_result_set   IN OUT SYS_REFCURSOR );

PROCEDURE update_salary
( p_employee_id IN employees.employee_id%TYPE,
p_new_salary  IN employees.salary%TYPE );

PROCEDURE change_job
( p_employee_id IN employees.employee_id%TYPE,
p_new_job     IN employees.job_id%TYPE,
p_new_salary  IN employees.salary%TYPE := NULL,
p_new_dept    IN employees.department_id%TYPE := NULL );

END employees_pkg;
/

See Also:

- "About the Application"

- "Creating and Managing Packages"

- Oracle Database PL/SQL Language Reference for information about the CREATE PACKAGE statement

Creating the Package Body for employees_pkg

Note:
You must be connected to Oracle Database Express Edition as user app_code.

To create the package body for employees_pkg, the API for managers, use the following CREATE PACKAGE BODY statement. You can enter the statement either in SQL*Plus or in the Worksheet of SQL Developer. Alternatively, you can create the package with the SQL Developer tool Create Body.

CREATE OR REPLACE PACKAGE BODY employees_pkg
AS
PROCEDURE get_employees_in_dept
( p_deptno     IN     employees.department_id%TYPE,
p_result_set IN OUT SYS_REFCURSOR )
IS
l_cursor SYS_REFCURSOR;
BEGIN
OPEN p_result_set FOR
SELECT e.employee_id,
e.first_name || ' ' || e.last_name name,
TO_CHAR( e.hire_date, 'Dy Mon ddth, yyyy' ) hire_date,
j.job_title,
m.first_name || ' ' || m.last_name manager,
d.department_name
FROM employees e INNER JOIN jobs j ON (e.job_id = j.job_id)
LEFT OUTER JOIN employees m ON (e.manager_id = m.employee_id)
INNER JOIN departments d ON (e.department_id = d.department_id)
WHERE e.department_id = p_deptno ;
END get_employees_in_dept;

PROCEDURE get_job_history
( p_employee_id  IN     employees.department_id%TYPE,
p_result_set   IN OUT SYS_REFCURSOR )
IS
BEGIN
OPEN p_result_set FOR
SELECT e.First_name || ' ' || e.last_name name, j.job_title,
e.job_start_date start_date,
TO_DATE(NULL) end_date
FROM employees e INNER JOIN jobs j ON (e.job_id = j.job_id)
WHERE e.employee_id = p_employee_id
UNION ALL
SELECT e.First_name || ' ' || e.last_name name,
j.job_title,
jh.start_date,
jh.end_date
FROM employees e INNER JOIN job_history jh
ON (e.employee_id = jh.employee_id)
INNER JOIN jobs j ON (jh.job_id = j.job_id)
WHERE e.employee_id = p_employee_id
ORDER BY start_date DESC;
END get_job_history;

PROCEDURE show_employee
( p_employee_id  IN     employees.employee_id%TYPE,
p_result_set   IN OUT sys_refcursor )
IS
BEGIN
OPEN p_result_set FOR
SELECT *
FROM (SELECT TO_CHAR(e.employee_id) employee_id,
e.first_name || ' ' || e.last_name name,
e.email_addr,
TO_CHAR(e.hire_date,'dd-mon-yyyy') hire_date,
e.country_code,
e.phone_number,
j.job_title,
TO_CHAR(e.job_start_date,'dd-mon-yyyy') job_start_date,
to_char(e.salary) salary,
m.first_name || ' ' || m.last_name manager,
d.department_name
FROM employees e INNER JOIN jobs j on (e.job_id = j.job_id)
RIGHT OUTER JOIN employees m ON (m.employee_id = e.manager_id)
INNER JOIN departments d ON (e.department_id = d.department_id)
WHERE e.employee_id = p_employee_id)
UNPIVOT (VALUE FOR ATTRIBUTE IN (employee_id, name, email_addr, hire_date,
country_code, phone_number, job_title, job_start_date, salary, manager,
department_name) );
END show_employee;

PROCEDURE update_salary
( p_employee_id IN employees.employee_id%type,
p_new_salary  IN employees.salary%type )
IS
BEGIN
UPDATE employees
SET salary = p_new_salary
WHERE employee_id = p_employee_id;
END update_salary;

PROCEDURE change_job
( p_employee_id IN employees.employee_id%TYPE,
p_new_job     IN employees.job_id%TYPE,
p_new_salary  IN employees.salary%TYPE := NULL,
p_new_dept    IN employees.department_id%TYPE := NULL )
IS
BEGIN
INSERT INTO job_history (employee_id, start_date, end_date, job_id,
department_id)
SELECT employee_id, job_start_date, TRUNC(SYSDATE), job_id, department_id
FROM employees
WHERE employee_id = p_employee_id;

UPDATE employees
SET job_id = p_new_job,
department_id = NVL( p_new_dept, department_id ),
salary = NVL( p_new_salary, salary ),
job_start_date = TRUNC(SYSDATE)
WHERE employee_id = p_employee_id;
END change_job;
END employees_pkg;
/

See Also:

- "About the Application"

- "Creating and Managing Packages"

- Oracle Database PL/SQL Language Reference for information about the CREATE PACKAGE BODY statement

Tutorial: Showing How the employees_pkg Subprograms Work

Using SQL*Plus, this tutorial shows how the subprograms of the employees_pkg package work. The tutorial also shows how the trigger employees_aiufer and the CHECK constraint job_history_date_check work.

Note:
You must be connected to Oracle Database Express Edition as user app_code from SQL*Plus.

To use SQL*Plus to show how the employees_pkg subprograms work:

1. Use formatting commands to improve the readability of the output. For example:

SET LINESIZE 80
SET RECSEP WRAPPED
SET RECSEPCHAR "="
COLUMN NAME FORMAT A15 WORD_WRAPPED
COLUMN HIRE_DATE FORMAT A20 WORD_WRAPPED
COLUMN DEPARTMENT_NAME FORMAT A10 WORD_WRAPPED
COLUMN JOB_TITLE FORMAT A29 WORD_WRAPPED
COLUMN MANAGER FORMAT A11 WORD_WRAPPED

2. Declare a bind variable for the value of the subprogram parameter p_result_set:

VARIABLE c REFCURSOR

3. Show the employees in department 90:

EXEC employees_pkg.get_employees_in_dept( 90, :c );
PRINT c

Result:

EMPLOYEE_ID NAME            HIRE_DATE            JOB_TITLE
----------- --------------- -------------------- --------------------------
MANAGER     DEPARTMENT
----------- ----------
100 Steven King     Tue Jun 17th, 2003   President
Executive                                                         ===========================================================================
102 Lex De Haan     Sat Jan 13th, 2001   Administration Vice President
Steven King Executive
===========================================================================
101 Neena Kochhar   Wed Sep 21st, 2005   Administration Vice President
Steven King Executive
===========================================================================

4. Show the job history of employee 101:

EXEC employees_pkg.get_job_history( 101, :c );
PRINT c

Result:

NAME            JOB_TITLE                     START_DAT END_DATE
--------------- ----------------------------- --------- ---------
Neena Kochhar   Administration Vice President 16-MAR-05
Neena Kochhar   Accounting Manager            28-OCT-01 15-MAR-05
Neena Kochhar   Public Accountant             21-SEP-97 27-OCT-01

5. Show general information about employee 101:

EXEC employees_pkg.show_employee( 101, :c );
PRINT c

Result:

ATTRIBUTE       VALUE
--------------- ----------------------------------------------
EMPLOYEE_ID     101
NAME            Neena Kochhar
EMAIL_ADDR      NKOCHHAR
HIRE_DATE       21-sep-2005
COUNTRY_CODE    +1
PHONE_NUMBER    515.123.4568
JOB_TITLE       Administration Vice President
JOB_START_DATE  16-mar-05
SALARY          17000
MANAGER         Steven King
DEPARTMENT_NAME Executive

11 rows selected.

6. Show the information about the job Administration Vice President:

SELECT * FROM jobs WHERE job_title = 'Administration Vice President';

Result:

JOB_ID     JOB_TITLE                     MIN_SALARY MAX_SALARY
---------- ----------------------------- ---------- ----------
AD_VP      Administration Vice President      15000      30000

7. Try to give employee 101 a new salary outside the range for her job:

EXEC employees_pkg.update_salary( 101, 30001 );

Result:

SQL> EXEC employees_pkg.update_salary( 101, 30001 );
BEGIN employees_pkg.update_salary( 101, 30001 ); END;

*
ERROR at line 1:
ORA-20002: Salary modification invalid
ORA-06512: at "APP_DATA.EMPLOYEES_AIUFER", line 13
ORA-04088: error during execution of trigger 'APP_DATA.EMPLOYEES_AIUFER'
ORA-06512: at "APP_CODE.EMPLOYEES_PKG", line 77
ORA-06512: at line 1

8. Give employee 101 a new salary inside the range for her job and show general information about her again:

EXEC employees_pkg.update_salary( 101, 18000 );
EXEC employees_pkg.show_employee( 101, :c );
PRINT c

Result:

ATTRIBUTE       VALUE
--------------- ----------------------------------------------
EMPLOYEE_ID     101
NAME            Neena Kochhar
EMAIL_ADDR      NKOCHHAR
HIRE_DATE       21-sep-2005
COUNTRY_CODE    +1
PHONE_NUMBER    515.123.4568
JOB_TITLE       Administration Vice President
JOB_START_DATE  16-mar-05
SALARY          18000
MANAGER         Steven King
DEPARTMENT_NAME Executive

11 rows selected.

9. Change the job of employee 101 to her current job with a lower salary:

EXEC employees_pkg.change_job( 101, 'AD_VP', 17500, 90 );

Result:

SQL> exec employees_pkg.change_job( 101, 'AD_VP', 17500, 90 );
BEGIN employees_pkg.change_job( 101, 'AD_VP', 17500, 80 ); END;

*
ERROR at line 1:
ORA-02290: check constraint (APP_DATA.JOB_HISTORY_DATE_CHECK) violated
ORA-06512: at "APP_CODE.EMPLOYEES_PKG", line 101
ORA-06512: at line 1

See Also:

- SQL*Plus User's Guide and Reference for information about SQL*Plus commands

- "Creating and Managing Packages"

Granting the Execute Privilege to app_user and app_user_admin

Note:
You must be connected to Oracle Database Express Edition as user app_code.

To grant the execute privilege on the package employees_pkg to app_user (typically a manager) and app_admin_user (an application administrator), use the following GRANT statements (in either order). You can enter the statements either in SQL*Plus or in the Worksheet of SQL Developer.

GRANT EXECUTE ON employees_pkg TO app_user;
GRANT EXECUTE ON employees_pkg TO app_admin_user;

See Also:

- "Schemas for the Application"

- Oracle Database SQL Language Reference for information about the GRANT statement

Tutorial: Invoking get_job_history as app_user or app_admin_user

Using SQL*Plus, this tutorial shows how to invoke the subprogram app_code.employees_pkg.get_job_history as the user app_user (typically a manager) or app_admin_user (an application administrator).

To invoke employees_pkg.get_job_history as app_user or app_admin_user:

1. Connect to Oracle Database Express Edition as user app_user or app_admin_user from SQL*Plus.
For instructions, see "Connecting to Oracle Database Express Edition from SQL*Plus".

2. Create this synonym:

CREATE SYNONYM employees_pkg FOR app_code.employees_pkg;

3. Show the job history of employee 101:

EXEC employees_pkg.get_job_history( 101, :c );
PRINT c

Result:

NAME            JOB_TITLE                     START_DAT END_DATE
--------------- ----------------------------- --------- ---------
Neena Kochhar   Administration Vice President 16-MAR-05 15-MAY-12
Neena Kochhar   Accounting Manager            28-OCT-01 15-MAR-05
Neena Kochhar   Public Accountant             21-SEP-97 27-OCT-01

Creating the admin_pkg Package

This section shows how to create the admin_pkg package, how its subprograms work, how to grant the execute privilege on the package to the user who needs it, and how that user can invoke one of its subprograms.

To create the admin_pkg package:

1. Connect to Oracle Database Express Edition as user app_admin.
For instructions, see either "Connecting to Oracle Database Express Edition from SQL*Plus" or "Connecting to Oracle Database Express Edition from SQL Developer".

2. Create these synonyms:

CREATE SYNONYM departments FOR app_data.departments;
CREATE SYNONYM jobs FOR app_data.jobs;
CREATE SYNONYM departments_sequence FOR app_data.departments_sequence;

You can enter the CREATE SYNONYM statements either in SQL*Plus or in the Worksheet of SQL Developer. Alternatively, you can create the tables with the SQL Developer tool Create Synonym.

3. Create the package specification.

4. Create the package body.

This section contains:

- Creating the Package Specification for admin_pkg

- Creating the Package Body for admin_pkg

- Tutorial: Showing How the admin_pkg Subprograms Work

- Granting the Execute Privilege to app_user_admin

- Tutorial: Invoking add_department as app_admin_user

See Also:

- "Creating and Managing Synonyms"

- "About Packages"

Creating the Package Specification for admin_pkg

Note:
You must be connected to Oracle Database Express Edition as user app_admin.

To create the package specification for admin_pkg, the API for application administrators, use the following CREATE PACKAGE statement. You can enter the statement either in SQL*Plus or in the Worksheet of SQL Developer. Alternatively, you can create the package with the SQL Developer tool Create Package.

CREATE OR REPLACE PACKAGE admin_pkg
AS
PROCEDURE update_job
( p_job_id      IN jobs.job_id%TYPE,
p_job_title   IN jobs.job_title%TYPE := NULL,
p_min_salary  IN jobs.min_salary%TYPE := NULL,
p_max_salary  IN jobs.max_salary%TYPE := NULL );

PROCEDURE add_job
( p_job_id      IN jobs.job_id%TYPE,
p_job_title   IN jobs.job_title%TYPE,
p_min_salary  IN jobs.min_salary%TYPE,
p_max_salary  IN jobs.max_salary%TYPE );

PROCEDURE update_department
( p_department_id     IN departments.department_id%TYPE,
p_department_name   IN departments.department_name%TYPE := NULL,
p_manager_id        IN departments.manager_id%TYPE := NULL,
p_update_manager_id IN BOOLEAN := FALSE );

FUNCTION add_department
( p_department_name   IN departments.department_name%TYPE,
p_manager_id        IN departments.manager_id%TYPE )
RETURN departments.department_id%TYPE;

END admin_pkg;
/

See Also:

- "About the Application"

- "Creating and Managing Packages"

- Oracle Database PL/SQL Language Reference for information about the CREATE PACKAGE statement

Creating the Package Body for admin_pkg

Note:
You must be connected to Oracle Database Express Edition as user app_admin.

To create the package body for admin_pkg, the API for application administrators, use the following CREATE PACKAGE BODY statement. You can enter the statement either in SQL*Plus or in the Worksheet of SQL Developer. Alternatively, you can create the package with the SQL Developer tool Create Body.

CREATE OR REPLACE PACKAGE BODY admin_pkg
AS
PROCEDURE update_job
( p_job_id      IN jobs.job_id%TYPE,
p_job_title   IN jobs.job_title%TYPE := NULL,
p_min_salary  IN jobs.min_salary%TYPE := NULL,
p_max_salary  IN jobs.max_salary%TYPE := NULL )
IS
BEGIN
UPDATE jobs
SET job_title  = NVL( p_job_title, job_title ),
min_salary = NVL( p_min_salary, min_salary ),
max_salary = NVL( p_max_salary, max_salary )
WHERE job_id = p_job_id;
END update_job;

PROCEDURE add_job
( p_job_id      IN jobs.job_id%TYPE,
p_job_title   IN jobs.job_title%TYPE,
p_min_salary  IN jobs.min_salary%TYPE,
p_max_salary  IN jobs.max_salary%TYPE )
IS
BEGIN
INSERT INTO jobs ( job_id, job_title, min_salary, max_salary )
VALUES ( p_job_id, p_job_title, p_min_salary, p_max_salary );
END add_job;

PROCEDURE update_department
( p_department_id     IN departments.department_id%TYPE,
p_department_name   IN departments.department_name%TYPE := NULL,
p_manager_id        IN departments.manager_id%TYPE := NULL,
p_update_manager_id IN BOOLEAN := FALSE )
IS
BEGIN
IF ( p_update_manager_id ) THEN
UPDATE departments
SET department_name = NVL( p_department_name, department_name ),
manager_id = p_manager_id
WHERE department_id = p_department_id;
ELSE
UPDATE departments
SET department_name = NVL( p_department_name, department_name )
WHERE department_id = p_department_id;
END IF;
END update_department;

FUNCTION add_department
( p_department_name   IN departments.department_name%TYPE,
p_manager_id        IN departments.manager_id%TYPE )
RETURN departments.department_id%TYPE
IS
l_department_id departments.department_id%TYPE;
BEGIN
INSERT INTO departments ( department_id, department_name, manager_id )
VALUES ( departments_sequence.NEXTVAL, p_department_name, p_manager_id );

RETURN l_department_id;
END add_department;

END admin_pkg;
/

See Also:

- "About the Application"

- "Creating and Managing Packages"

- Oracle Database PL/SQL Language Reference for information about the CREATE PACKAGE BODY statement

Tutorial: Showing How the admin_pkg Subprograms Work

Using SQL*Plus, this tutorial shows how the subprograms of the admin_pkg package work. The tutorial also shows how the trigger jobs_aufer works.

Note:
You must be connected to Oracle Database Express Edition as user app_admin from SQL*Plus.

To show how the admin_pkg subprograms work:

1. Show the information about the job whose ID is AD_VP:

SELECT * FROM jobs WHERE job_id = 'AD_VP';

Result:

JOB_ID     JOB_TITLE                           MIN_SALARY MAX_SALARY
---------- ----------------------------------- ---------- ----------
AD_VP      Administration Vice President            15000      30000

2. Increase the maximum salary for this job and show the information about it again:

EXEC admin_pkg.update_job( 'AD_VP', p_max_salary => 31000 );
SELECT * FROM jobs WHERE job_id = 'AD_VP';

Result:

JOB_ID     JOB_TITLE                           MIN_SALARY MAX_SALARY
---------- ----------------------------------- ---------- ----------
AD_VP      Administration Vice President            15000      31000

3. Show the information about the job whose ID is IT_PROG:

SELECT * FROM jobs WHERE job_id = 'IT_PROG';

Result:

JOB_ID     JOB_TITLE                           MIN_SALARY MAX_SALARY
---------- ----------------------------------- ---------- ----------
IT_PROG    Programmer                                4000      10000

4. Try to increase the minimum salary for this job:

EXEC admin_pkg.update_job( 'IT_PROG', p_max_salary => 4001 );

Result (from SQL*Plus):

SQL> EXEC admin_pkg.update_job( 'IT_PROG', p_max_salary => 4001 );
BEGIN admin_pkg.update_job( 'IT_PROG', p_max_salary => 4001 ); END;

*
ERROR at line 1:
ORA-20001: Salary update would violate 5 existing employee records
ORA-06512: at "APP_DATA.JOBS_AUFER", line 12
ORA-04088: error during execution of trigger 'APP_DATA.JOBS_AUFER'
ORA-06512: at "APP_ADMIN.ADMIN_PKG", line 10
ORA-06512: at line 1

5. Add a new job and show the information about it:

EXEC admin_pkg.add_job( 'AD_CLERK', 'Administrative Clerk', 3000, 7000 );
SELECT * FROM jobs WHERE job_id = 'AD_CLERK';

Result:

JOB_ID     JOB_TITLE                           MIN_SALARY MAX_SALARY
---------- ----------------------------------- ---------- ----------
AD_CLERK   Administrative Clerk                      3000       7000

6. Show the information about department 100:

SELECT * FROM departments WHERE department_id = 100;

Result:

DEPARTMENT_ID DEPARTMENT_NAME                MANAGER_ID
------------- ------------------------------ ----------
100 Finance                               108

7. Change the name and manager of department 100 and show the information about it:

EXEC admin_pkg.update_department( 100, 'Financial Services' );
EXEC admin_pkg.update_department( 100, p_manager_id => 111,
p_update_manager_id => true );
SELECT * FROM departments WHERE department_id = 100;

Result:

DEPARTMENT_ID DEPARTMENT_NAME                MANAGER_ID
------------- ------------------------------ ----------
100 Financial Services                    111

See Also:
"Creating and Managing Packages"

Granting the Execute Privilege to app_user_admin

Note:
You must be connected to Oracle Database Express Edition as user app_admin.

To grant the execute privilege on the package admin_pkg to app_admin_user (an application administrator), use the following GRANT statement. You can enter the statement either in SQL*Plus or in the Worksheet of SQL Developer.

GRANT EXECUTE ON admin_pkg TO app_admin_user;

See Also:

- "Schemas for the Application"

- Oracle Database SQL Language Reference for information about the GRANT statement

Tutorial: Invoking add_department as app_admin_user

Using SQL*Plus, this tutorial shows how to invoke the function app_admin.admin_pkg.add_department as the user app_admin_user (an application administrator) and then see the information about the new department.

To invoke admin_pkg.add_department as app_admin_user:

1. Connect to Oracle Database Express Edition as user app_admin_user from SQL*Plus.
For instructions, see "Connecting to Oracle Database Express Edition from SQL*Plus".

2. Create this synonym:

CREATE SYNONYM admin_pkg FOR app_admin.admin_pkg;

3. Declare a bind variable for the return value of the function:

VARIABLE n NUMBER

4. Add a new department without a manager:

EXEC :n := admin_pkg.add_department( 'New department', NULL );

5. Show the ID of the manager of the new department:

PRINT :n

Result:

N
----------
275

To see the information about the new department:

1. Connect to Oracle Database Express Edition as user app_admin.

2. Show the information about the new department:

SELECT * FROM departments WHERE department_name LIKE 'New department%';

Result:

DEPARTMENT_ID DEPARTMENT_NAME                MANAGER_ID
------------- ------------------------------ ----------
275 New department

10 Deploying an Oracle Database Express Edition Application

This chapter contains:

- About Development and Deployment Environments

- About Installation Scripts

- Creating Installation Scripts

- Deploying the Sample Application

- Checking the Validity of an Installation

- Archiving the Installation Scripts

About Development and Deployment Environments

The database on which you develop your application is called the development environment. After developing your application, you can install it on other databases, called deployment environments, where other users can run it.

The first deployment environment is the test environment. In the test environment, you can thoroughly test the functionality of the application, determine whether it is structured correctly, and fix any problems before deploying it in the production environment.

You might also deploy your application to an education environment, either before or after deploying it to the production environment. An education environment provides a place for users to practice running the application without affecting other environments.

If the desired deployment environments do not exist in your organization, you can create them.

About Installation Scripts

A script is a series of SQL statements in a file whose name ends with .sql (for example, create_app.sql). When you run a script in a client program such as SQL*Plus or SQL Developer, the SQL statements run in the order in which they appear in the script. A script whose SQL statements create an application is called an installation script. An installation script can either have all the SQL statements needed to create the application or it can be a master script that runs other scripts.

To deploy an application, you run one or more installation scripts in the deployment environment. For a new application, you must create the installation scripts. For an older application, the installation scripts might exist, but if they do not, you can create them.

This section contains:

- About DDL Statements and Schema Object Dependencies

- About INSERT Statements and Constraints

About DDL Statements and Schema Object Dependencies

An installation script contains DDL statements that create schema objects and, optionally, INSERT statements that load data into the tables that its DDL statements create.

To create installation scripts correctly, and to run multiple installation scripts in the correct order, you must understand the dependencies between the schema objects of your application.

If the definition of object A references object B, then A depends on B. Therefore, you must create B before you create A. Otherwise, the statement that creates B either fails or creates B in an invalid state, depending on the object type.

For a complex application, the order for creating the objects is rarely obvious. Usually, you must consult the database designer or a diagram of the design.

See Also:

- Oracle Database Advanced Application Developer's Guide for more information about schema object dependencies

- "About Data Definition Language (DDL) Statements"

About INSERT Statements and Constraints

When you run an installation script that contains INSERT statements, the INSERT statements insert data from the source tables (in the development environment) into the corresponding new tables in the deployment environment. For each source table in your application, you must determine whether any constraints could be violated when their data is inserted in the new table. If so, you must first disable those constraints, then insert the data, and then try to re-enable the constraints. If a data item violates a constraint, then you cannot re-enable that constraint until you correct the data item.

If you are simply inserting lookup data in correct order (as in "Loading the Data"), then constraints are not violated. Therefore, you do not need to disable them first.

If you are inserting data from an outside source (such as a file, spreadsheet, or older application), or from many tables that have much dependent data, disable the constraints before inserting the data.

Some possible ways to disable and re-enable the constraints are:

- Using SQL Developer, disable and re-enable the constraints one at a time:

1. In the Connections frame, select the appropriate table.

2. In the pane labeled with table name, select the subtab Constraints.

3. In the list of all constraints on the table, change ENABLED to DISABLED (or the reverse).

- Edit the installation script, adding SQL statements that disable and re-enable each constraint.

- Create a SQL script with SQL statements that disable and enable each constraint.

- Find the constraints in the Oracle Database Express Edition data dictionary, and create a SQL script with the SQL statements to disable and enable each constraint.
For example, to find and enable the constraints used in the EVALUATIONS, PERFORMANCE_PARTS, and SCORES tables from "Creating Tables", enter these statements into the Worksheet:

SELECT 'ALTER TABLE '|| TABLE_NAME || ' DISABLE CONSTRAINT '||
CONSTRAINT_NAME ||';'
FROM user_constraints
WHERE table_name IN ('EVALUATIONS','PERFORMANCE_PARTS','SCORES');

SELECT 'ALTER TABLE '|| TABLE_NAME || ' ENABLE CONSTRAINT '||
CONSTRAINT_NAME ||';'
FROM user_constraints
WHERE table_name IN ('EVALUATIONS','PERFORMANCE_PARTS','SCORES');

See Also:

- "About the INSERT Statement"

- "Ensuring Data Integrity in Tables"

Creating Installation Scripts

If an installation script needs only DDL and INSERT statements, then you can create it with either SQL Developer or any text editor. In SQL Developer, you can use either the Cart or the Database Export wizard. Oracle recommends the Cart for installation scripts that you expect to run in multiple deployment environments and the Database Export wizard for installation scripts that you expect to run in only one deployment environment.

If an installation script needs SQL statements that are neither DDL nor INSERT statements, then you must create it with a text editor.

This section explains how to create installation scripts with the Cart and the Database Export wizard, when and how to edit installation scripts that create sequences and triggers, and how create installation scripts for the application in Chapter 9, "Developing a Simple Oracle Database Express Edition Application" ("the sample application").

This section contains:

- Creating Installation Scripts with the Cart

- Creating an Installation Script with the Database Export Wizard

- Editing Installation Scripts that Create Sequences

- Editing Installation Scripts that Create Triggers

- Creating Installation Scripts for the Sample Application

Creating Installation Scripts with the Cart

The Cart is a convenient tool for deploying Oracle Database Express Edition objects from one or more database connections to a destination connection. You drag and drop objects from the navigator frame into the Cart window, specify the desired options, and click the Export Cart icon to display the Export Objects dialog box. After you complete the information in that dialog box, SQL Developer creates a .zip file containing scripts (including a master script) to create the objects in the schema of a desired destination connection.

To create installation scripts with the Cart:

1. In the SQL Developer window, click the menu View.

2. From the View menu, select Cart.
The Cart window opens. The Export Cart icon is inactive (gray).

Tip:
In the Cart window, for information about Cart user preferences, press the key F1.

3. In the Connections frame, select the schema objects that you want the installation script to create and drag them into the Cart window.
In The Cart window, the Export Cart icon is now active (not gray).

4. For each Selected Object of Type TABLE, if you want the installation script to export data, then select the option Data.

5. Click Export Cart.

6. In the Export Objects dialog box, enter the desired values in the fields.
For information about these fields, see Oracle SQL Developer User's Guide.

7. Click Apply.
SQL Developer creates a .zip file containing scripts (including a master script) to create the objects in the schema of a desired destination connection.

8. In the master script and the scripts that it runs, check that:

- Referenced objects are created before their dependent objects.

- Tables are created before data is inserted into them.

If the installation scripts create sequences, see "Editing Installation Scripts that Create Sequences".

If the installation scripts create triggers, see "Editing Installation Scripts that Create Sequences".

If necessary, edit the installation files in the Worksheet or any text editor.

See Also:
Oracle SQL Developer User's Guide for more information about the Cart

Creating an Installation Script with the Database Export Wizard

To create an installation script in SQL Developer with the Database Export wizard, you specify the name of the installation script, the objects and data to export, and the desired options, and the wizard generates an installation script.

Note:
In the following procedure, you might have to enlarge the SQL Developer windows to see all fields and options.

To create an installation script with the Database Export wizard:

1. If you have not done so, create a directory for the installation script, separate from the Oracle Database Express Edition installation directory (for example, C:\my_exports).

2. In the SQL Developer window, click the menu Tools.

3. From the menu, select Database Export.

4. In the Export Wizard - Step 1 of 5 (Source/Destination) window:

1. In the Connection field, select your connection to the development environment.

2. Select the desired Export DDL options (and deselect any selected undesired options).

Note:
Do not deselect Terminator, or the installation script will fail.

3. If you do not want the installation script to export data, then deselect Export Data.

4. In the Save As field, accept the default Single File and type the full path name of the installation script (for example, C:\my_exports\hr_export.sql).
The file name must end with .sql.

5. Click Next.

5. In the Export Wizard - Step 2 of 5 (Types to Export) window:

1. Deselect the check boxes for the types that you do not want to export.
Selecting or deselecting Toggle All selects or deselects all check boxes.

2. Click Next.

6. In the Export Wizard - Step 3 of 5 (Specify Objects) window:

1. Click More.

2. In the Schema field, select your schema from the menu.

3. In the Type field, select from the menu either ALL OBJECTS or a specific object type (for example, TABLE).

4. Click Lookup.
A list of objects appears in the left frame. If the value of the Type field is ALL OBJECTS, then the list contains all objects in the selected schema. If the value of the Type field is a specific object type, then the list contains all objects of that type in the selected schema.

5. Move the objects that you want to export from the left frame to the right frame:

To move all objects, click >>. (To move all objects back, click <<.)

To move selected objects, select them and then click >. (To move selected objects back, select them and click <.)

6. (Optional) Repeat steps 3 through 5 for other object types.

7. Click Next.
If you deselected Export Data in the Source/Destination window, then the Export Summary window appears—go to step 3.

If you did not deselect Export Data in the Source/Destination window, then the Export Wizard - Step 4 of 5 (Specify Data) window appears. The lower frame lists the objects that you specified in the Specify Objects window.

7. In the Specify Data window:

1. Move the objects whose data you do not want to export from the lower frame to the upper frame:
To move all objects, click the double upward arrow icon. (To move all objects back, click the double downward arrow icon.)

To move selected objects, select them and then click the single upward arrow icon.

2. Click Next.

8. In the Export Wizard - Step 5 of 5 (Export Summary) window, click Finish.

The Exporting window opens, showing that exporting is occurring. When exporting is complete, the Exporting window closes, and the Worksheet shows the contents of the installation script that you specified in the Source/Destination window.

9. In the installation script, check that:

- Referenced objects are created before their dependent objects.

- Tables are created before data is inserted into them.

If necessary, edit the file in the Worksheet or any text editor.

See Also:
Oracle SQL Developer User's Guide for more information about the Database Export wizard

Editing Installation Scripts that Create Sequences

For a sequence, SQL Developer generates a CREATE SEQUENCE statement whose START WITH value is relative to the current value of the sequence in the development environment.

If your application uses the sequence to generate unique keys, and you will not insert the data from the source tables into the corresponding new tables, then you might want to edit the START WITH value in the installation script.

You can edit the installation script in either the Worksheet or any text editor.

See Also:
"Tutorial: Creating a Sequence"

Editing Installation Scripts that Create Triggers

If your application has a BEFORE INSERT trigger on a source table, and you will insert the data from that source table into the corresponding new table, then you must decide if you want the trigger to fire before each INSERT statement in the installation script inserts data into the new table.

For example, NEW_EVALUATION_TRIGGER (created in "Tutorial: Creating a Trigger that Generates a Primary Key for a Row Before It Is Inserted") fires before a row is inserted into the EVALUATIONS table. The trigger generates the unique number for the primary key of that row, using EVALUATIONS_SEQUENCE.

The source EVALUATIONS table is populated with primary keys. If you do not want the installation script to put new primary key values in the new EVALUATIONS table, then you must edit the CREATE TRIGGER statement in the installation script as shown in bold font:

CREATE OR REPLACE
TRIGGER NEW_EVALUATION_TRIGGER
BEFORE INSERT ON EVALUATIONS
FOR EACH ROW
BEGIN
IF :NEW.evaluation_id IS NULL THEN
:NEW.evaluation_id := evaluations_sequence.NEXTVAL
END IF;
END;

Also, if the current value of the sequence is not greater than the maximum value in the primary key column, then you must make it greater.

You can edit the installation script in either the Worksheet or any text editor.

Two alternatives to editing the installation script are:

- Change the trigger definition in the source file and then re-create the installation script.
For information about changing triggers, see "Changing Triggers".

- Disable the trigger before running the data installation script, and then re-enable it afterward.
For information about disabling and enabling triggers, see "Disabling and Enabling Triggers".

See Also:
"Creating Triggers"

Creating Installation Scripts for the Sample Application

This section explains how to create the following installation scripts for the application in Chapter 9, "Developing a Simple Oracle Database Express Edition Application" ("the sample application"):

- schemas.sql, which does in the deployment environment what you did in the development environment in "Creating the Schemas for the Application" and "Granting Privileges to the Schemas"

- objects.sql, which does in the deployment environment what you did in the development environment in "Creating the Schema Objects and Loading the Data"

- employees.sql, which does in the deployment environment what you did in the development environment in "Creating the employees_pkg Package"

- admin.sql, which does in the deployment environment what you did in the development environment in "Creating the admin_pkg Package"

- create_app.sql, a master script that runs the preceding scripts, thereby deploying the sample application in the deployment environment

You can create the scripts in any order. To create schemas.sql and create_app.sql, you must use a text editor. To create the other scripts, you can use either a text editor or SQL Developer.

This section contains:

- Creating Installation Script schemas.sql

- Creating Installation Script objects.sql

- Creating Installation Script employees.sql

- Creating Installation Script admin.sql

- Creating Master Installation Script create_app.sql

Creating Installation Script schemas.sql

The installation script schemas.sql does in the deployment environment what you did in the development environment in "Creating the Schemas for the Application" and "Granting Privileges to the Schemas".

To create schemas.sql, enter the following text in any text editor and save the file as schemas.sql.

Caution:
Choose secure passwords. For guidelines for secure passwords, see Oracle Database Security Guide.

-----------------
-- Create schemas
-----------------

DROP USER app_data CASCADE;

CREATE USER app_data IDENTIFIED BY password
DEFAULT TABLESPACE USERS
QUOTA UNLIMITED ON USERS
ENABLE EDITIONS;

DROP USER app_code CASCADE;

CREATE USER app_code IDENTIFIED BY password
DEFAULT TABLESPACE USERS
QUOTA UNLIMITED ON USERS
ENABLE EDITIONS;

DROP USER app_admin CASCADE;

CREATE USER app_admin IDENTIFIED BY password
DEFAULT TABLESPACE USERS
QUOTA UNLIMITED ON USERS
ENABLE EDITIONS;

DROP USER app_user CASCADE;

CREATE USER app_user IDENTIFIED BY password
ENABLE EDITIONS;

DROP USER app_admin_user CASCADE;

CREATE USER app_admin_user IDENTIFIED BY password
ENABLE EDITIONS;

------------------------------
-- Grant privileges to schemas
------------------------------

GRANT CREATE SESSION TO app_data;
GRANT CREATE TABLE, CREATE VIEW, CREATE TRIGGER, CREATE SEQUENCE TO app_data;
GRANT SELECT ON HR.DEPARTMENTS TO app_data;
GRANT SELECT ON HR.EMPLOYEES TO app_data;
GRANT SELECT ON HR.JOB_HISTORY TO app_data;
GRANT SELECT ON HR.JOBS TO app_data;

GRANT CREATE SESSION, CREATE PROCEDURE, CREATE SYNONYM TO app_code;

GRANT CREATE SESSION, CREATE PROCEDURE, CREATE SYNONYM TO app_admin;

GRANT CREATE SESSION, CREATE SYNONYM TO app_user;

GRANT CREATE SESSION, CREATE SYNONYM TO app_admin_user;

See Also:
"Schemas for the Application" for descriptions of the schemas for the sample application

Creating Installation Script objects.sql

The installation script objects.sql does in the deployment environment what you did in the development environment in "Creating the Schema Objects and Loading the Data".

You can create objects.sql using either a text editor or SQL Developer.

To create objects.sql in any text editor, enter the following text and save the file as objects.sql. For password, use the password that schema.sql specifies when it creates the user app_data.

Note:
The INSERT statements that load the data work only if the deployment environment has a standard HR schema. If it does not, then either use SQL Developer to create a script that loads the new tables (in the deployment environment) with data from the source tables (in the development environment) or modify the INSERT statements in the following script.

------------------------
-- Create schema objects
------------------------

CONNECT app_data/password

CREATE TABLE jobs#
( job_id      VARCHAR2(10)
CONSTRAINT jobs_pk PRIMARY KEY,
job_title   VARCHAR2(35)
CONSTRAINT jobs_job_title_not_null NOT NULL,
min_salary  NUMBER(6)
CONSTRAINT jobs_min_salary_not_null NOT NULL,
max_salary  NUMBER(6)
CONSTRAINT jobs_max_salary_not_null NOT NULL
)
/

CREATE TABLE departments#
( department_id    NUMBER(4)
CONSTRAINT departments_pk PRIMARY KEY,
department_name  VARCHAR2(30)
CONSTRAINT dept_department_name_not_null NOT NULL
CONSTRAINT dept_department_name_unique UNIQUE,
manager_id       NUMBER(6)
)
/

CREATE TABLE employees#
( employee_id     NUMBER(6)
CONSTRAINT employees_pk PRIMARY KEY,
first_name      VARCHAR2(20)
CONSTRAINT emp_first_name_not_null NOT NULL,
last_name       VARCHAR2(25)
CONSTRAINT emp_last_name_not_null NOT NULL,
email_addr      VARCHAR2(25)
CONSTRAINT emp_email_addr_not_null NOT NULL,
hire_date       DATE
DEFAULT TRUNC(SYSDATE)
CONSTRAINT emp_hire_date_not_null NOT NULL
CONSTRAINT emp_hire_date_check
CHECK(TRUNC(hire_date) = hire_date),
country_code    VARCHAR2(5)
CONSTRAINT emp_country_code_not_null NOT NULL,
phone_number    VARCHAR2(20)
CONSTRAINT emp_phone_number_not_null NOT NULL,
job_id          CONSTRAINT emp_job_id_not_null NOT NULL
CONSTRAINT emp_to_jobs_fk REFERENCES jobs#,
job_start_date  DATE
CONSTRAINT emp_job_start_date_not_null NOT NULL,
CONSTRAINT emp_job_start_date_check
CHECK(TRUNC(JOB_START_DATE) = job_start_date),
salary          NUMBER(6)
CONSTRAINT emp_salary_not_null NOT NULL,
manager_id      CONSTRAINT emp_mgrid_to_emp_empid_fk REFERENCES employees#,
department_id   CONSTRAINT emp_to_dept_fk REFERENCES departments#
)
/

CREATE TABLE job_history#
( employee_id  CONSTRAINT job_hist_to_emp_fk REFERENCES employees#,
job_id       CONSTRAINT job_hist_to_jobs_fk REFERENCES jobs#,
start_date   DATE
CONSTRAINT job_hist_start_date_not_null NOT NULL,
end_date     DATE
CONSTRAINT job_hist_end_date_not_null NOT NULL,
department_id
CONSTRAINT job_hist_to_dept_fk REFERENCES departments#
CONSTRAINT job_hist_dept_id_not_null NOT NULL,
CONSTRAINT job_history_pk PRIMARY KEY(employee_id,start_date),
CONSTRAINT job_history_date_check CHECK( start_date < end_date )
)
/

CREATE EDITIONING VIEW jobs AS SELECT * FROM jobs#
/
CREATE EDITIONING VIEW departments AS SELECT * FROM departments#
/
CREATE EDITIONING VIEW employees AS SELECT * FROM employees#
/
CREATE EDITIONING VIEW job_history AS SELECT * FROM job_history#
/

CREATE OR REPLACE TRIGGER employees_aiufer
AFTER INSERT OR UPDATE OF salary, job_id ON employees FOR EACH ROW
DECLARE
l_cnt NUMBER;
BEGIN
LOCK TABLE jobs IN SHARE MODE;  -- Ensure that jobs does not change
-- during the following query.
SELECT COUNT(*) INTO l_cnt
FROM jobs
WHERE job_id = :NEW.job_id
AND :NEW.salary BETWEEN min_salary AND max_salary;

IF (l_cnt<>1) THEN
RAISE_APPLICATION_ERROR( -20002,
CASE
WHEN :new.job_id = :old.job_id
THEN 'Salary modification invalid'
ELSE 'Job reassignment puts salary out of range'
END );
END IF;
END;
/

CREATE OR REPLACE TRIGGER jobs_aufer
AFTER UPDATE OF min_salary, max_salary ON jobs FOR EACH ROW
WHEN (NEW.min_salary > OLD.min_salary OR NEW.max_salary < OLD.max_salary)
DECLARE
l_cnt NUMBER;
BEGIN
LOCK TABLE employees IN SHARE MODE;

SELECT COUNT(*) INTO l_cnt
FROM employees
WHERE job_id = :NEW.job_id
AND salary NOT BETWEEN :NEW.min_salary and :NEW.max_salary;

IF (l_cnt>0) THEN
RAISE_APPLICATION_ERROR( -20001,
'Salary update would violate ' || l_cnt || ' existing employee records' );
END IF;
END;
/

CREATE SEQUENCE employees_sequence START WITH 210;
CREATE SEQUENCE departments_sequence START WITH 275;

------------
-- Load data
------------

INSERT INTO jobs (job_id, job_title, min_salary, max_salary)
SELECT job_id, job_title, min_salary, max_salary
FROM HR.JOBS
/

INSERT INTO departments (department_id, department_name, manager_id)
SELECT department_id, department_name, manager_id
FROM HR.DEPARTMENTS
/

INSERT INTO employees (employee_id, first_name, last_name, email_addr,
hire_date, country_code, phone_number, job_id, job_start_date, salary,
manager_id, department_id)
SELECT employee_id, first_name, last_name, email, hire_date,
CASE WHEN phone_number LIKE '011.%'
THEN '+' || SUBSTR( phone_number, INSTR( phone_number, '.' )+1,
INSTR( phone_number, '.', 1, 2 ) -  INSTR( phone_number, '.' ) - 1 )
ELSE '+1'
END country_code,
CASE WHEN phone_number LIKE '011.%'
THEN SUBSTR( phone_number, INSTR(phone_number, '.', 1, 2 )+1 )
ELSE phone_number
END phone_number,
job_id,
NVL( (SELECT MAX(end_date+1)
FROM HR.JOB_HISTORY jh
WHERE jh.employee_id = employees.employee_id), hire_date),
salary, manager_id, department_id
FROM HR.EMPLOYEES
/

INSERT INTO job_history (employee_id, job_id, start_date, end_date,
department_id)
SELECT employee_id, job_id, start_date, end_date, department_id
FROM HR.JOB_HISTORY
/

COMMIT;

-----------------------------
-- Add foreign key constraint
-----------------------------

ALTER TABLE departments#
ADD CONSTRAINT dept_to_emp_fk
FOREIGN KEY(manager_id) REFERENCES employees#;

----------------------------------------------
-- Grant privileges on schema objects to users
----------------------------------------------

GRANT SELECT, INSERT, UPDATE, DELETE ON employees TO app_code;
GRANT SELECT ON departments TO app_code;
GRANT SELECT ON jobs TO app_code;
GRANT SELECT, INSERT on job_history TO app_code;
GRANT SELECT ON employees_sequence TO app_code;

GRANT SELECT, INSERT, UPDATE, DELETE ON jobs TO app_admin;
GRANT SELECT, INSERT, UPDATE, DELETE ON departments TO app_admin;
GRANT SELECT ON employees_sequence TO app_admin;
GRANT SELECT ON departments_sequence TO app_admin;

GRANT SELECT ON jobs TO app_admin_user;
GRANT SELECT ON departments TO app_admin_user;

See Also:

- "Schema Objects of the Application" for descriptions of the schema objects of the sample application

- "Creating Installation Scripts with the Cart"

- "Creating an Installation Script with the Database Export Wizard"

Creating Installation Script employees.sql

The installation script employees.sql does in the deployment environment what you did in the development environment in "Creating the employees_pkg Package".

You can create employees.sql using either a text editor or SQL Developer.

To create employees.sql in any text editor, enter the following text and save the file as employees.sql. For password, use the password that schema.sql specifies when it creates the user app_code.

-----------------------
-- Create employees_pkg
-----------------------

CONNECT app_code/password

CREATE SYNONYM employees FOR app_data.employees;
CREATE SYNONYM departments FOR app_data.departments;
CREATE SYNONYM jobs FOR app_data.jobs;
CREATE SYNONYM job_history FOR app_data.job_history;

CREATE OR REPLACE PACKAGE employees_pkg
AS
PROCEDURE get_employees_in_dept
( p_deptno     IN     employees.department_id%TYPE,
p_result_set IN OUT SYS_REFCURSOR );

PROCEDURE get_job_history
( p_employee_id  IN     employees.department_id%TYPE,
p_result_set   IN OUT SYS_REFCURSOR );

PROCEDURE show_employee
( p_employee_id  IN     employees.employee_id%TYPE,
p_result_set   IN OUT SYS_REFCURSOR );

PROCEDURE update_salary
( p_employee_id IN employees.employee_id%TYPE,
p_new_salary  IN employees.salary%TYPE );

PROCEDURE change_job
( p_employee_id IN employees.employee_id%TYPE,
p_new_job     IN employees.job_id%TYPE,
p_new_salary  IN employees.salary%TYPE := NULL,
p_new_dept    IN employees.department_id%TYPE := NULL );
END employees_pkg;
/

CREATE OR REPLACE PACKAGE BODY employees_pkg
AS
PROCEDURE get_employees_in_dept
( p_deptno     IN     employees.department_id%TYPE,
p_result_set IN OUT SYS_REFCURSOR )
IS
l_cursor SYS_REFCURSOR;
BEGIN
OPEN p_result_set FOR
SELECT e.employee_id,
e.first_name || ' ' || e.last_name name,
TO_CHAR( e.hire_date, 'Dy Mon ddth, yyyy' ) hire_date,
j.job_title,
m.first_name || ' ' || m.last_name manager,
d.department_name
FROM employees e INNER JOIN jobs j ON (e.job_id = j.job_id)
LEFT OUTER JOIN employees m ON (e.manager_id = m.employee_id)
INNER JOIN departments d ON (e.department_id = d.department_id)
WHERE e.department_id = p_deptno ;
END get_employees_in_dept;

PROCEDURE get_job_history
( p_employee_id  IN     employees.department_id%TYPE,
p_result_set   IN OUT SYS_REFCURSOR )
IS
BEGIN
OPEN p_result_set FOR
SELECT e.First_name || ' ' || e.last_name name, j.job_title,
e.job_start_date start_date,
TO_DATE(NULL) end_date
FROM employees e INNER JOIN jobs j ON (e.job_id = j.job_id)
WHERE e.employee_id = p_employee_id
UNION ALL
SELECT e.First_name || ' ' || e.last_name name,
j.job_title,
jh.start_date,
jh.end_date
FROM employees e INNER JOIN job_history jh
ON (e.employee_id = jh.employee_id)
INNER JOIN jobs j ON (jh.job_id = j.job_id)
WHERE e.employee_id = p_employee_id
ORDER BY start_date DESC;
END get_job_history;

PROCEDURE show_employee
( p_employee_id  IN     employees.employee_id%TYPE,
p_result_set   IN OUT sys_refcursor )
IS
BEGIN
OPEN p_result_set FOR
SELECT *
FROM (SELECT TO_CHAR(e.employee_id) employee_id,
e.first_name || ' ' || e.last_name name,
e.email_addr,
TO_CHAR(e.hire_date,'dd-mon-yyyy') hire_date,
e.country_code,
e.phone_number,
j.job_title,
TO_CHAR(e.job_start_date,'dd-mon-yyyy') job_start_date,
to_char(e.salary) salary,
m.first_name || ' ' || m.last_name manager,
d.department_name
FROM employees e INNER JOIN jobs j on (e.job_id = j.job_id)
RIGHT OUTER JOIN employees m ON (m.employee_id = e.manager_id)
INNER JOIN departments d ON (e.department_id = d.department_id)
WHERE e.employee_id = p_employee_id)
UNPIVOT (VALUE FOR ATTRIBUTE IN (employee_id, name, email_addr, hire_date,
country_code, phone_number, job_title, job_start_date, salary, manager,
department_name) );
END show_employee;

PROCEDURE update_salary
( p_employee_id IN employees.employee_id%type,
p_new_salary  IN employees.salary%type )
IS
BEGIN
UPDATE employees
SET salary = p_new_salary
WHERE employee_id = p_employee_id;
END update_salary;

PROCEDURE change_job
( p_employee_id IN employees.employee_id%TYPE,
p_new_job     IN employees.job_id%TYPE,
p_new_salary  IN employees.salary%TYPE := NULL,
p_new_dept    IN employees.department_id%TYPE := NULL )
IS
BEGIN
INSERT INTO job_history (employee_id, start_date, end_date, job_id,
department_id)
SELECT employee_id, job_start_date, TRUNC(SYSDATE), job_id, department_id
FROM employees
WHERE employee_id = p_employee_id;

UPDATE employees
SET job_id = p_new_job,
department_id = NVL( p_new_dept, department_id ),
salary = NVL( p_new_salary, salary ),
job_start_date = TRUNC(SYSDATE)
WHERE employee_id = p_employee_id;
END change_job;
END employees_pkg;
/

---------------------------------------------
-- Grant privileges on employees_pkg to users
---------------------------------------------

GRANT EXECUTE ON employees_pkg TO app_user;
GRANT EXECUTE ON employees_pkg TO app_admin_user;

See Also:

- "Creating Installation Scripts with the Cart"

- "Creating an Installation Script with the Database Export Wizard"

Creating Installation Script admin.sql

The installation script admin.sql does in the deployment environment what you did in the development environment in "Creating the admin_pkg Package".

You can create admin.sql using either a text editor or SQL Developer.

To create admin.sql in any text editor, enter the following text and save the file as admin.sql. For password, use the password that schema.sql specifies when it creates the user app_admin.

-------------------
-- Create admin_pkg
-------------------

CONNECT app_admin/password

CREATE SYNONYM departments FOR app_data.departments;
CREATE SYNONYM jobs FOR app_data.jobs;
CREATE SYNONYM departments_sequence FOR app_data.departments_sequence;

CREATE OR REPLACE PACKAGE admin_pkg
AS
PROCEDURE update_job
( p_job_id      IN jobs.job_id%TYPE,
p_job_title   IN jobs.job_title%TYPE := NULL,
p_min_salary  IN jobs.min_salary%TYPE := NULL,
p_max_salary  IN jobs.max_salary%TYPE := NULL );

PROCEDURE add_job
( p_job_id      IN jobs.job_id%TYPE,
p_job_title   IN jobs.job_title%TYPE,
p_min_salary  IN jobs.min_salary%TYPE,
p_max_salary  IN jobs.max_salary%TYPE );

PROCEDURE update_department
( p_department_id     IN departments.department_id%TYPE,
p_department_name   IN departments.department_name%TYPE := NULL,
p_manager_id        IN departments.manager_id%TYPE := NULL,
p_update_manager_id IN BOOLEAN := FALSE );

FUNCTION add_department
( p_department_name   IN departments.department_name%TYPE,
p_manager_id        IN departments.manager_id%TYPE )
RETURN departments.department_id%TYPE;

END admin_pkg;
/

CREATE OR REPLACE PACKAGE BODY admin_pkg
AS
PROCEDURE update_job
( p_job_id      IN jobs.job_id%TYPE,
p_job_title   IN jobs.job_title%TYPE := NULL,
p_min_salary  IN jobs.min_salary%TYPE := NULL,
p_max_salary  IN jobs.max_salary%TYPE := NULL )
IS
BEGIN
UPDATE jobs
SET job_title  = NVL( p_job_title, job_title ),
min_salary = NVL( p_min_salary, min_salary ),
max_salary = NVL( p_max_salary, max_salary )
WHERE job_id = p_job_id;
END update_job;

PROCEDURE add_job
( p_job_id      IN jobs.job_id%TYPE,
p_job_title   IN jobs.job_title%TYPE,
p_min_salary  IN jobs.min_salary%TYPE,
p_max_salary  IN jobs.max_salary%TYPE )
IS
BEGIN
INSERT INTO jobs ( job_id, job_title, min_salary, max_salary )
VALUES ( p_job_id, p_job_title, p_min_salary, p_max_salary );
END add_job;

PROCEDURE update_department
( p_department_id     IN departments.department_id%TYPE,
p_department_name   IN departments.department_name%TYPE := NULL,
p_manager_id        IN departments.manager_id%TYPE := NULL,
p_update_manager_id IN BOOLEAN := FALSE )
IS
BEGIN
IF ( p_update_manager_id ) THEN
UPDATE departments
SET department_name = NVL( p_department_name, department_name ),
manager_id = p_manager_id
WHERE department_id = p_department_id;
ELSE
UPDATE departments
SET department_name = NVL( p_department_name, department_name )
WHERE department_id = p_department_id;
END IF;
END update_department;

FUNCTION add_department
( p_department_name   IN departments.department_name%TYPE,
p_manager_id        IN departments.manager_id%TYPE )
RETURN departments.department_id%TYPE
IS
l_department_id departments.department_id%TYPE;
BEGIN
INSERT INTO departments ( department_id, department_name, manager_id )
VALUES ( departments_sequence.NEXTVAL, p_department_name, p_manager_id );

RETURN l_department_id;
END add_department;

END admin_pkg;
/

----------------------------------------
-- Grant privileges on admin_pkg to user
----------------------------------------

GRANT EXECUTE ON admin_pkg TO app_admin_user;

See Also:

- "Creating Installation Scripts with the Cart"

- "Creating an Installation Script with the Database Export Wizard"

Creating Master Installation Script create_app.sql

The master installation script create_app.sql runs the other four installation scripts for the sample application in the correct order, thereby deploying the sample application in the deployment environment.

To create create_app.sql, enter the following text in any text editor and save the file as create_app.sql:

@schemas.sql
@objects.sql
@employees.sql
@admin.sql

Deploying the Sample Application

This section explains how to deploy the sample application using the installation scripts that you created in "Creating Installation Scripts for the Sample Application".

Note:
For the following procedures, you need the name and password of a user who has the CREATE USER and DROP USER system privileges.

To deploy the sample application using SQL*Plus:

1. Copy the installation scripts that you created in "Creating Installation Scripts for the Sample Application" to the deployment environment.

2. In the deployment environment, connect to Oracle Database Express Edition as a user with the CREATE USER and DROP USER system privileges.

3. At the SQL> prompt, run the master installation script:

@create_app.sql

The master installation script runs the other four installation scripts for the sample application in the correct order, thereby deploying the sample application in the deployment environment.

To deploy the sample application using SQL Developer:

1. If necessary, create a connection to the deployment environment.
For Connection Name, enter a name that is not the name of the connection to the development environment.

2. Copy the installation scripts that you created in "Creating Installation Scripts for the Sample Application" to the deployment environment.

3. Connect to Oracle Database Express Edition as a user with the CREATE USER and DROP USER system privileges in the deployment environment.
A new pane appears. On its tab is the name of the connection to the deployment environment. The pane has two subpanes, Worksheet and Query Builder.

4. In the Worksheet pane, type the command for running the master installation script:

@create_app.sql

5. Click the icon Run Script.
The master installation script runs the other four installation scripts for the sample application in the correct order, thereby deploying the sample application in the deployment environment. The output appears in the Script Output pane, under the Worksheet pane.

In the Connections frame, if you expand the connection to the deployment environment, and then expand the type of each object that the sample application uses, you see the objects of the sample application.

See Also:

- SQL*Plus User's Guide and Reference for more information about using scripts in SQL*Plus

- Oracle SQL Developer User's Guide for more information about running scripts in SQL Developer

Checking the Validity of an Installation

After installing your application in a deployment environment, you can check its validity in the following ways in SQL Developer:

- In the Connections frame:

1. Expand the connection to the deployment environment.

2. Examine the definitions of the new objects.

- In the Reports pane:

1. Expand Data Dictionary Reports.
A list of data dictionary reports appears.

2. Expand All Objects.
A list of objects reports appears.

3. Select All Objects.
The Select Connection window appears.

4. In the Connection field, select from the menu the connection to the deployment environment.

5. Click OK.

6. In the Enter Bind Values window, select either Owner or Object Name.

7. Click Apply.
The message "Displaying Results" shows, followed by the results.

For each object, this report lists the Owner, Object Type, Object Name, Status (Valid or Invalid), Date Created, and Last DDL. Last DDL is the date of the last DDL operation that affected the object.

8. In the Reports pane, select Invalid Objects.

9. In the Enter Bind Values window, click Apply.
For each object whose Status is Invalid, this report lists the Owner, Object Type, and Object Name.

See Also:
Oracle SQL Developer User's Guide for more information about SQL Developer reports

Archiving the Installation Scripts

After verifying that the installation of your application is valid, Oracle recommends that you archive your installation scripts in a source code control system. Before doing so, add comments to each file, documenting its creation date and purpose. If you ever must deploy the same application to another environment, you can use these archived files.

See Also:
Oracle Database Utilities for information about Oracle Data Pump, which enables very high-speed movement of data and metadata from one database to another

Index
A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W

Symbols

%FOUND cursor attribute, 5.9.4

%ISOPEN cursor attribute, 5.9.4

%NOTFOUND cursor attribute, 5.9.4

%ROWCOUNT cursor attribute, 5.9.4

%ROWTYPE attribute, 5.9.1

%TYPE attribute

purpose of, 5.7.2

tutorial for, 5.7.3

A

accent-insensitive sort, 7.5.12

accessing Oracle Database, 1.3.2

See also connecting to Oracle Database

Add Check tool, 4.2.3.2 Add Foreign Key tool, 4.2.3.2 Add Primary Key tool, 4.2.3.2 Add Unique tool, 4.2.3.2 AFTER trigger, 6.1

statement-level example, 6.2.2

system example, 6.2.5

aggregate conversion function in query, 2.6.9.7 alias

for column, 2.6.5

for table, 2.6.8

See also synonym

ALTER FUNCTION statement, 5.5.4 ALTER PROCEDURE statement, 5.5.4 ALTER TABLE statement

adding constraint with

Foreign Key, 4.2.3.2

Not Null, 4.2.3.2

Primary Key, 4.2.3.2

changing trigger status with, 6.4.2 ALTER TRIGGER statement

changing trigger status with, 6.4.1

recompiling trigger with, 6.5

anonymous block, 5.1 application program interface (API), 5.6.1, 5.6.1 archiving installation script, 10.6 arithmetic operator in query, 2.6.9.1 array

associative

See associative array

variable, 5.10.1 ASP.NET, 1.3.2.5.9 assignment operator &(colon;=)

assigning initial value to constant with, 5.7

assigning value to associative array element with, 5.10.2

assigning value to variable with, 5.7.4.1

See also SELECT INTO statement

associative array, 5.10.2

declaring, 5.10.3

dense, 5.10.2

indexed by integer, 5.10.2

indexed by string, 5.10.2

populating, 5.10.4

sparse, 5.10.2

traversing

dense, 5.10.5

sparse, 5.10.6

attribute

%ROWTYPE, 5.9.1

%TYPE

purpose of, 5.7.2

tutorial for, 5.7.3

cursor

See cursor attribute

B

base type, 5.4

basic LOOP statement, 5.8.6

BEFORE trigger, 6.1

row-level example, 6.2.3

system example, 6.2.5

bind argument, 8.1.2 block

anonymous, 5.1

parts of, 1.3.2.4

body of subprogram, 5.5.1 browsing HR sample schema, 2.5.1 built-in data type, 4.2.1 BULK COLLECT INTO clause, 5.10.4 bulk SQL, 8.1.3.5 byte semantics, 7.1.7

C

C numeric format element, 7.5.10

calendar format, 7.1.4

Cart, 10.3.1

CASE expression in query, 2.6.9.9

case sensitivity

in PL/SQL identifiers, 5.3

in sort, 7.5.12

CASE statement, 5.8.3 character function in query, 2.6.9.4 character semantics, 7.1.7 character set

conversion and data loss, 7.6.2

length semantics and, 7.1.7

Check Constraint, 4.2.3.1

adding with Add Check tool, 4.2.3.2

checking validity of installation, 10.5 CLR (Common Language Runtime), 1.3.2.5.9 collapsing displayed information in SQL Developer, 2.5.1 collating sequence, 7.1.6 collection, 5.10.1 collection method, 5.10.1

COUNT, 5.10.5

FIRST, 5.10.6

invoking, 5.10.1

NEXT, 5.10.6

column

alias for, 2.6.5

new heading for, 2.6.5

qualifying name of, 2.6.8

relationship to field, 1.3.1

selecting specific one in table, 2.6.4

comment in PL/SQL code, 5.5.1 Commit Changes icon, 3.3 COMMIT statement

explicit, 3.3

implicit, 3.3

committing transaction

explicitly, 3.3

implicitly, 3.3

Common Language Runtime (CLR), 1.3.2.5.9 comparing programming methods, 8.1.6 composite variable

collection, 5.10.1

record, 5.9.1

compound trigger, 6.1 concatenation operator in query, 2.6.9.3 concurrency, 8.1.4 concurrent sessions, 8.1.5 conditional predicate, 6.2.2 conditional selection statement, 5.8.1

CASE, 5.8.3

IF, 5.8.2

connecting to Oracle Database

as user HR, 2.3

from SQL Developer, 2.2

from SQL*Plus, 2.1

constant, 5.7

declaring, 5.7.1

ensuring correct data type of, 5.7.2

in package body, 5.7

in package specification, 5.7

local, 5.7

constraint, 4.2.3

adding to table

with ALTER TABLE statement, 4.2.3.2

with Edit Table tool, 4.2.3.2

application deployment and, 10.2.2 enabled or disabled, 4.2.3 types of, 4.2.3.1 viewing, 2.5.2 controlling program flow, 5.8 conversion function in query, 2.6.9.6 COUNT collection method, 5.10.5 Create Body tool, 5.6.4 Create Database Synonym tool, 4.5.1 CREATE FUNCTION statement, 5.5.3 Create Function tool, 5.5.3 CREATE INDEX statement

changing index with, 4.2.7.2

creating index with, 4.2.7.1

Create Index tool, 4.2.7.1 CREATE PACKAGE BODY statement, 5.6.4 CREATE PACKAGE statement

changing package specification with, 5.6.3

creating package specification with, 5.6.2

Create Package tool, 5.6.2 CREATE PROCEDURE statement, 5.5.2 Create Procedure tool, 5.5.2 CREATE SEQUENCE statement, 4.4.1

in installation script, 10.3.3

Create Sequence tool, 4.4.1 CREATE SYNONYM statement, 4.5.1 CREATE TABLE statement, 4.2.2.2 Create Table tool, 4.2.2.1 CREATE TRIGGER statement

changing trigger with, 6.3

creating trigger with, 6.2

Create Trigger tool, 6.2 CREATE VIEW statement

changing query in view with, 4.3.2

creating view with, 4.3.1.2

Create View tool, 4.3.1.1 creation script

See installation script

CURRVAL pseudocolumn, 4.4 cursor, 5.9.4

declared, 5.9.4

declaring associative array with, 5.10.3

implicit, 5.9.4

populating associative array with, 5.10.4

cursor attribute, 5.9.4

%FOUND, 5.9.4

%ISOPEN, 5.9.4

%NOTFOUND, 5.9.4

%ROWCOUNT, 5.9.4

possible values of, 5.9.4

syntax for value of, 5.9.4

cursor variable, 5.9.7

disadvantages of, 8.1.3.3

retrieving result set rows one at a time with

procedure, 5.9.8

tutorial, 5.9.9

D

data concurrency, 8.1.4

data consistency, 8.1.4

data definition language statement

See DDL statement

data integrity

See constraint

data loss during character-set conversion, 7.6.2 data manipulation language statement

See DML statement

Data pane, 4.2.5 data type

base, 5.4

built-in, 4.2.1

of associative array key, 5.10.2

of constant, 5.4

of function return value, 5.4

of subprogram parameter, 5.4

of table column, 4.2.1

of variable, 5.4

PL/SQL, 5.4

SQL, 4.2.1

SQL national character, 7.1.8

subtype of, 5.4

Unicode, 7.1.8

user-defined, 4.2.1

Database Export wizard, 10.3.2 database initialization parameter, 7.2 date format, 7.1.3 datetime format model, 2.6.9.6 datetime function in query, 2.6.9.5 DBMS_APPLICATION_INFO package, 8.2.1 DBMS_OUTPUT.PUT_LINE procedure, 5.8.3 DBMS_SESSION package, 8.2.1 DBMS_SQL package, 8.1.3.4 DBMS_STANDARD.RAISE_APPLICATION_ERROR procedure, 5.11.1 DDL statement, 4.1

as triggering event, 6.1

decimal character, 7.5.8 declarative language, 1.3.2.3 declarative part

of block, 1.3.2.4

of subprogram, 5.5.1

declared cursor, 5.9.4

advantages over cursor variable, 8.1.3.3

retrieving result set rows one at a time with, 5.9.5

DECODE function in query, 2.6.9.10 Delete Selected Row(s) tool, 4.2.6 DELETE statement, 3.1.3 DELETING conditional predicate, 6.2.2 deleting entire table, 4.2.8 deleting row from table

with Delete Selected Row(s) tool, 4.2.6

with DELETE statement, 3.1.3

dense associative array, 5.10.2

populating, 5.10.4

traversing, 5.10.5

dependencies between schema objects

installation and, 10.2.1

trigger compilation and, 6.5

deploying application, 10 deployment environment, 10.1 development environment, 10.1

choice of, 1.3.2.5

disabled trigger, 6.1 disabling triggers, 6.4

all triggers in table, 6.4.2

in installation script, 10.3.4

DL (long date) format, 7.5.4 DML statement, 3.1

as triggering event, 6.1

associative arrays and, 5.10.2

implicit cursor for, 5.9.4

dot notation

for accessing record field, 5.9.1

for invoking collection method, 5.10.1

DROP FUNCTION statement, 5.5.6 DROP INDEX statement, 4.2.7.2, 4.2.7.3 DROP PACKAGE statement, 5.6.5 DROP PROCEDURE statement, 5.5.6 DROP SEQUENCE statement, 4.4.2 DROP SYNONYM statement, 4.5.2 DROP TABLE statement, 4.2.8 Drop tool

for index, 4.2.7.3

for package, 5.6.5

for sequence, 4.4.2

for synonym, 4.5.2, 5.5.6

for table, 4.2.8

for trigger, 6.6

for view, 4.3.4

DROP TRIGGER statement, 6.6 DROP VIEW statement, 4.3.4 DS (short date) format, 7.5.4 DUAL table, 2.6.9.5

E

Edit Index tool, 4.2.7.2

Edit Table tool, 4.2.3.2

Edit tool

changing standalone subprogram with, 5.5.4

changing trigger with, 6.3

editioning view, 8.2.4

in sample application, 9.4.2

education environment, 10.1 enabled trigger, 6.1 enabling triggers, 6.4

all triggers in table, 6.4.2

in installation script, 10.3.4

ending transaction

by committing, 3.3

by rolling back, 3.4

ensuring data integrity, 4.2.3 environment variables, 7.4 error

See exception

exception handler syntax, 5.11.1 exception handling, 5.11.1

for predefined exception, 5.11.3

EXCEPTION_INIT pragma, 5.11.1 exception-handling part

of block, 1.3.2.4

of subprogram, 5.5.1

executable part

of block, 1.3.2.4

of subprogram, 5.5.1

EXECUTE IMMEDIATE statement, 8.1.3.2 exhaustion of resources, 8.1.1 EXIT WHEN statement, 5.8.6 expanding displayed information in SQL Developer, 2.5.1 exploring Oracle Database

with SQL Developer, 2.5

with SQL*Plus, 2.4

expression in query, 2.6.9

F

FCL (Framework Class Libraries), 1.3.2.5.9

FETCH statement

explicit cursor and, 5.9.4

populating dense associative array with, 5.10.4

fetching results one row at a time, 5.9.4 field, 5.9.1

relationship to column, 1.3.1

FIRST collection method, 5.10.6 FOR LOOP statement, 5.8.4 Foreign Key constraint, 4.2.3.1

adding

to sample application, 9.4.6

with Add Foreign Key tool, 4.2.3.2

with ALTER TABLE statement, 4.2.3.2

format

calendar, 7.1.4

date, 7.1.3

datetime model, 2.6.9.6

monetary, 7.1.5

time, 7.1.3

Framework Class Libraries (FCL), 1.3.2.5.9 function, 5.1

in query, 2.6.9

locale-dependent SQL, 7.4.2

statistical, 2.6.9.7

structure of, 5.5.1

See also subprogram

G

G numeric format element, 7.5.8

globalization support features, 7.1

See also NLS parameters

group separator in number, 7.5.8 grouping query results, 2.6.9.7

H

hard parse, 8.1.2

HR sample schema, 1.4

browsing, 2.5.1

unlocking, 2.3.1

Hypertext Preprocessor (PHP), 1.3.2.5.3

I

icon names and keyboard equivalents, 1.3.2.2

identifier, 5.3

IF statement, 5.8.2

implicit COMMIT statement, 3.3

implicit cursor, 5.9.4

index, 1.3.1

adding, 4.2.7.1

changing, 4.2.7.2

dropping, 4.2.7.3

implicitly created, 4.2.7

index-by table

See associative array

initial value of constant or variable, 5.7 initialization parameter, 7.2 Insert Row tool, 4.2.4 INSERT statement, 3.1.1

in sample application, 9.4.5

INSERTING conditional predicate, 6.2.2 installation script, 10.2

archiving, 10.6

creating, 10.3

disabling and re-enabling triggers in, 10.3.4

editing CREATE SEQUENCE statement in, 10.3.3

INSTEAD OF trigger, 6.1

example, 6.2.4

instrumentation package, 8.2.1 integrity constraint

See constraint

intersecting tables, 2.6.8 invalidated trigger, 6.5 IW date format element, 7.1.4

J

JDBC (Oracle Java Database Connectivity), 1.3.2.5.2

joining tables, 2.6.8

K

keyboard equivalents of icons, 1.3.2.2

key-value pair

See associative array

L

L numeric format element, 7.5.9

language support, 7.1.1

latch, 8.1.4.2

length semantics, 7.1.7

linguistic sorting and string searching, 7.1.6

loading data

See INSERT statement

local constant, 5.7 local subprogram

in anonymous block, 5.1

in another subprogram, 5.1

in package, 5.6.1

local variable, 5.7 locale, 7.5.1 locale-dependent SQL function, 7.4.2 logical table

See view

long date (DL) format, 7.5.4 loop statement, 5.8.1

basic LOOP, 5.8.6

exiting early, 5.8.6

FOR LOOP, 5.8.4

populating associative array with, 5.10.4

WHILE LOOP, 5.8.5

M

master script

See installation script

method, 5.10.1 Microsoft .NET Framework, 1.3.2.5.9 Microsoft Visual Studio, 1.3.2.5.9 monetary format, 7.1.5 multiline comment in PL/SQL code, 5.5.1 multilingual applications, 7.1

N

naming convention

for sequences, 4.4

in sample application, 9.1.3

national character set, 7.1.8 National Language Support (NLS), 7.1 National Language Support (NLS) parameters

See NLS parameters

native language support, 7.1.1 NCHAR literal replacement, 7.6.2 nested subprogram

See local subprogram

nested table, 5.10.1 .NET assembly, 1.3.2.5.9 .NET stored procedure, 1.3.2.5.9 NEW pseudorecord, 6.2.1 NEXT collection method, 5.10.6 NEXTVAL pseudocolumn, 4.4 NLS (National Language Support), 7.1 NLS environment variables, 7.4 NLS parameters

of locale-dependent SQL functions, 7.4.2

values of

changing, 7.4

initial, 7.2

viewing, 7.3

what they are, 7.1 NLS_CALENDAR parameter, 7.5.7 NLS_COMP parameter, 7.5.13 NLS_CURRENCY parameter, 7.5.9 NLS_DATE_FORMAT parameter, 7.5.4 NLS_DATE_LANGUAGE parameter, 7.5.5 NLS_DUAL_CURRENCY parameter, 7.5.11 NLS_ISO_CURRENCY parameter, 7.5.10 NLS_LANG parameter, 7.5.1 NLS_LANGUAGE parameter, 7.5.2 NLS_LENGTH_SEMANTICS parameter, 7.5.14 NLS_NUMERIC_CHARACTERS parameter, 7.5.8 NLS_SORT parameter, 7.5.12 NLS_TERRITORY parameter, 7.5.3 NLS_TIMESTAMP_FORMAT parameter, 7.5.6 nonblocking reads and writes, 8.1.4.3 nonprocedural language, 1.3.2.3 Not Null constraint, 4.2.3.1

adding

with ALTER TABLE statement, 4.2.3.2

with Edit Table tool, 4.2.3.2

numeric format

elements

C, 7.5.10

G, 7.5.8

L, 7.5.9

in different countries, 7.1.5 numeric function in query, 2.6.9.2 NVL function, 2.6.9.8 NVL2 function, 2.6.9.8

O

objects

See schema object

OCCI (Oracle C++ Call Interface), 1.3.2.5.5 OCI (Oracle Call Interface), 1.3.2.5.4 ODBC (Open Database Connectivity), 1.3.2.5.6 ODP.NET, 1.3.2.5.9 ODT (Oracle Developer Tools for Visual Studio), 1.3.2.5.9 OLD pseudorecord, 6.2.1 Open Database Connectivity (ODBC), 1.3.2.5.6 OPEN FOR statement, 8.1.3.3 OR REPLACE clause in DDL statement, 4.1 Oracle Application Express, 1.3.2.5.1 Oracle C++ Call Interface (OCCI), 1.3.2.5.5 Oracle Call Interface (OCI), 1.3.2.5.4 Oracle Database Extensions for .NET, 1.3.2.5.9 Oracle Deployment Wizard for .NET, 1.3.2.5.9 Oracle Developer Tools for Visual Studio, 1.3.2.5.9 Oracle Java Database Connectivity (JDBC), 1.3.2.5.2 Oracle Provider for OLE DB (OraOLEDB), 1.3.2.5.10 Oracle Providers for ASP.NET, 1.3.2.5.9 OraOLEDB (Oracle Provider for OLE DB), 1.3.2.5.10 ORDER BY clause of SELECT statement, 2.6.7

P

package, 5.2

dropping, 5.6.5

in sample application

admin_pkg, 9.6

employees_pkg, 9.5

instrumentation, 8.2.1 reasons to use, 5.2 structure of, 5.6.1 package body, 5.6.1

changing, 5.7.1

creating, 5.6.4

package specification, 5.6.1

changing, 5.6.3

creating, 5.6.2

package subprogram, 5.1 parameter

See subprogram parameter

parse, 8.1.2 PHP (Hypertext Preprocessor), 1.3.2.5.3 PLS_INTEGER data type, 5.4 PL/SQL block

anonymous, 5.1

parts of, 1.3.2.4

PL/SQL data type, 5.4 PL/SQL identifier, 5.3 PL/SQL language, 1.3.2.4

scalability and, 8.1.3

PL/SQL table

See associative array

PL/SQL unit, 1.3.2.4 precompiler

Pro*C/C++, 1.3.2.5.7

Pro*COBOL, 1.3.2.5.8

predefined exception, 5.11.1

handling, 5.11.3

Primary Key constraint, 4.2.3.1

adding

with Add Primary Key tool, 4.2.3.2

with ALTER TABLE statement, 4.2.3.2

private SQL area, 5.9.4 privileges

for schemas of sample application, 9.3

for users of sample application

on admin_pkg, 9.6

on employees_pkg, 9.5.4, 9.6.4

on schema objects, 9.4.7

security and, 8.3 Pro*C/C++ precompiler, 1.3.2.5.7 Pro*COBOL precompiler, 1.3.2.5.8 Procedural Language/SQL (PL/SQL) language, 1.3.2.4 procedure, 5.1

structure of, 5.5.1

See also subprogram

production environment, 10.1 program flow control, 5.8 programming practices, recommended, 8.2 pseudorecord, 6.2.1

Q

qualifying column names, 2.6.8

query, 2.6.1

function in, 2.6.9

grouping results by column, 2.6.9.7

improving readability of, 2.6.8

operator in, 2.6.9

simple, 2.6.1

SQL expression in, 2.6.9

stored

See view

R

RAISE statement, 5.11.1

RAISE_APPLICATION_ERROR procedure, 5.11.1

recommended programming practices, 8.2

record, 5.9.1

creating, 5.9.1

creating type for, 5.9.2

relationship to row, 1.3.1

reducing disk input/output (I/O), 4.2.7 REF constraint, 4.2.3.1 REF CURSOR type, 5.9.7 REF CURSOR variable

See cursor variable

Refresh icon

DDL statements and, 4.1

DML statements and, 3.1

rolling back transactions and, 3.4

RENAME statement, 4.3.3 Rename tool, 4.3.3 resetting password of HR account, 2.3.1 resource exhaustion, 8.1.1 retrieving results one row at a time, 5.9.4 RETURN clause of function, 5.5.1 RETURN statement, 5.5.1 return type

of cursor variable, 5.9.7

of function, 5.4

of REF CURSOR type, 5.9.7

reversing transaction, 3.4 Rollback Changes icon, 3.4 ROLLBACK statement, 3.4 rolling back transaction, 3.4 row

adding

with Insert Row tool, 4.2.4

with INSERT statement, 3.1.1

relationship to record, 1.3.1 row-level trigger, 6.1

example, 6.2.3

pseudorecords and, 6.2.1

Run tool, 5.5.5 Runstats tool, 8.1.6 runtime error

See exception

S

sample application

deploying, 10.4

developing, 9

sample schema HR

See HR sample schema, 1.4

SAVEPOINT statement, 3.5 scalable application, 8.1.1 schema, 1.3

in sample application

creating, 9.2

description of, 9.1.2.2

privileges for, 9.3

schema object, 1.3

creating and managing, 4

dependent

installation and, 10.2.1

trigger compilation and, 6.5

in sample application

creating, 9.4

description of, 9.1.2.1

schema-level subprogram

See standalone subprogram

script

See installation script

searched CASE expression, 2.6.9.9 searched CASE statement, 5.8.3 security

bind arguments and, 8.1.2

in sample application, 9.1.2.2

privileges and, 8.3

SELECT INTO statement

assigning value to variable with, 5.7.4.2

implicit cursor for, 5.9.4

See also assignment operator &(colon;=)

SELECT statement

ORDER BY clause of, 2.6.7

simple, 2.6.1

WHERE clause of, 2.6.6

selecting table data, 2.6.1

and sorting it, 2.6.7

that matches specified conditions, 2.6.6

semantics

byte, 7.1.7

character, 7.1.7

length, 7.1.7

sequence, 4.4

creating, 4.4.1

for sample application, 9.4.4

dropping, 4.4.2 improving data concurrency with, 8.1.4.1 in installation script, 10.3.3 sequential control statement, 5.8.1 serializable transaction, 8.1.4 setting savepoints in transaction, 3.5 shared SQL, 8.1.4.4 short date (DS) format, 7.5.4 signature of subprogram, 5.5.1 simple CASE expression, 2.6.9.9 simple CASE statement, 5.8.3 simple trigger, 6.1 single-line comment in PL/SQL code, 5.5.1 soft parse, 8.1.2 sorting

accent-insensitive, 7.5.12

case-insensitive, 7.5.12

linguistic, 7.1.6

selected data, 2.6.7

sparse associative array, 5.10.2

populating, 5.10.4

traversing, 5.10.6

SQL cursor (implicit cursor), 5.9.4 SQL data type, 4.2.1 SQL Developer, 1.3.2.2

collapsing displayed information in, 2.5.1

connecting to Oracle Database from, 2.2

as user HR, 2.3.3

expanding displayed information in, 2.5.1 exploring database with, 2.5 icon names and keyboard equivalents in, 1.3.2.2 initial values of NLS parameters in, 7.2 SQL expression in query, 2.6.9 SQL injection attack, 8.1.2 SQL language, 1.3.2.3 SQL national data types, 7.1.8 SQL*Plus, 1.3.2.1

connecting to Oracle Database from, 2.1

as user HR, 2.3.2

exploring database with, 2.4 standalone subprogram, 5.1

changing, 5.5.4

creating

function, 5.5.3

procedure, 5.5.2

dropping, 5.5.6 statement-level trigger, 6.1

example, 6.2.2

statistical function, 2.6.9.7 statistics

for comparing programming techniques, 8.1.6.1

for database, 8.2.2

stored query

See view

stored subprogram, 5.1 strong REF CURSOR type, 5.9.7 strongly typed cursor variable, 5.9.7, 5.9.7 struct type

See record

Structured Query Language (SQL), 1.3.2.3 subprogram, 5.1

body of, 5.5.1

local

See local subprogram

nested

See local subprogram

package, 5.1 parameter of

See subprogram parameter

parts of, 5.5.1 schema-level

See standalone subprogram

signature of, 5.5.1 standalone

See standalone subprogram

stored, 5.1 structure of, 5.5.1 subprogram parameter

collection as, 5.10.1

cursor variable as, 5.9.7

ensuring correct data type of, 5.7.2

record as, 5.9.1

subquery, 2.6.1 subscript notation, 5.10.1 subtype, 5.4 synonym, 4.5

creating, 4.5.1

dropping, 4.5.2

See also alias

SYS_REFCURSOR predefined type, 5.9.7 SYSDATE function, 2.6.9.5 system trigger, 6.1

example, 6.2.5

SYSTIMESTAMP function, 2.6.9.5

T

table, 4.2

adding constraint to

with ALTER TABLE statement, 4.2.3.2

with Edit Table tool, 4.2.3.2

adding row to

with Insert Row tool, 4.2.4

with INSERT statement, 3.1.1

alias for, 2.6.8 changing data in

in Data pane, 4.2.5

with UPDATE statement, 3.1.2

creating, 4.2.2

for sample application, 9.4.1

deleting row from

with Delete Selected Row(s) tool, 4.2.6

with DELETE statement, 3.1.3

dropping, 4.2.8 ensuring data integrity in, 4.2.3 index on

See index

logical

See view

selecting data from, 2.6.1

and sorting it, 2.6.7

that matches specified conditions, 2.6.6

selecting specific columns of, 2.6.4 viewing properties and data of

with SQL Developer, 2.5.2

with SQL*Plus, 2.4.2

virtual

See view

territory support, 7.1.2 test environment, 10.1 time format, 7.1.3 timing point of trigger, 6.1 transaction, 3.2

committing

explicitly, 3.3

implicitly, 3.3

ending

by committing, 3.3

by rolling back, 3.4

rolling back, 3.4 serializable, 8.1.4 setting savepoints in, 3.5 visibility of, 3.3 transaction control statement, 3.2 trigger, 6.1

AFTER, 6.1

statement-level example, 6.2.2

system example, 6.2.5

BEFORE, 6.1

row-level example, 6.2.3

system example, 6.2.5

changing, 6.3 compiling, 6.5 compound, 6.1 creating, 6.2

for sample application, 9.4.3

disabled, 6.1 disabling, 6.4

in installation script, 10.3.4

dropping, 6.6 enabled, 6.1 enabling, 6.4

in installation script, 10.3.4

INSTEAD OF, 6.1

example, 6.2.4

invalidated, 6.5 on view, 6.2.4 recompiling, 6.5 row-level, 6.1

example, 6.2.3

pseudorecords and, 6.2.1

simple, 6.1 statement-level, 6.1

example, 6.2.2

system, 6.1

example, 6.2.5

timing point of, 6.1

U

undoing transaction, 3.4

Unicode, 7.1.8

data types for, 7.1.8

string literals in, 7.6.1

Unique constraint, 4.2.3.1

adding with Add Unique tool, 4.2.3.2

unlocking HR account, 2.3.1 unscalable application, 8.1.1 UPDATE statement, 3.1.2 UPDATING conditional predicate, 6.2.2 user-defined data type, 4.2.1 user-defined exception, 5.11.1 UTL_FILE package, 8.2.1

V

validity of installation, 10.5

variable, 5.7

assigning value to

with assignment operator, 5.7.4.1

with SELECT INTO statement, 5.7.4.2

composite

collection, 5.10.1

record, 5.9.1

cursor

See cursor variable

declaring, 5.7.1 ensuring correct data type of, 5.7.2 in package body, 5.7 in package specification, 5.7 local, 5.7 variable array (varray), 5.10.1 view, 4.3

changing name of, 4.3.3

changing query in, 4.3.2

creating, 4.3.1

for sample application, 9.4.2

dropping, 4.3.4 trigger on, 6.2.4 viewing table properties and data

with SQL Developer, 2.5.2

with SQL*Plus, 2.4.2

virtual table

See view

visibility of transaction, 3.3 Visual Studio, 1.3.2.5.9

W

warehousing system, 8.1.2

weak REF CURSOR type, 5.9.7

WHEN OTHERS exception handler, 5.11.1

WHERE clause of SELECT statement, 2.6.6

WHILE LOOP statement, 5.8.5

Oracle Legal Notices

Copyright Notice

Copyright © 1994-2014, Oracle and/or its affiliates. All rights reserved.

Trademark Notice

Oracle and Java are registered trademarks of Oracle and/or its affiliates. Other names may be trademarks of their respective owners.

Intel and Intel Xeon are trademarks or registered trademarks of Intel Corporation. All SPARC trademarks are used under license and are trademarks or registered trademarks of SPARC International, Inc. AMD, Opteron, the AMD logo, and the AMD Opteron logo are trademarks or registered trademarks of Advanced Micro Devices. UNIX is a registered trademark of The Open Group.

License Restrictions Warranty/Consequential Damages Disclaimer

This software and related documentation are provided under a license agreement containing restrictions on use and disclosure and are protected by intellectual property laws. Except as expressly permitted in your license agreement or allowed by law, you may not use, copy, reproduce, translate, broadcast, modify, license, transmit, distribute, exhibit, perform, publish, or display any part, in any form, or by any means. Reverse engineering, disassembly, or decompilation of this software, unless required by law for interoperability, is prohibited.

Warranty Disclaimer

The information contained herein is subject to change without notice and is not warranted to be error-free. If you find any errors, please report them to us in writing.

Restricted Rights Notice

If this is software or related documentation that is delivered to the U.S. Government or anyone licensing it on behalf of the U.S. Government, the following notice is applicable:

U.S. GOVERNMENT END USERS: Oracle programs, including any operating system, integrated software, any programs installed on the hardware, and/or documentation, delivered to U.S. Government end users are "commercial computer software" pursuant to the applicable Federal Acquisition Regulation and agency-specific supplemental regulations. As such, use, duplication, disclosure, modification, and adaptation of the programs, including any operating system, integrated software, any programs installed on the hardware, and/or documentation, shall be subject to license terms and license restrictions applicable to the programs. No other rights are granted to the U.S. Government.

Hazardous Applications Notice

This software or hardware is developed for general use in a variety of information management applications. It is not developed or intended for use in any inherently dangerous applications, including applications that may create a risk of personal injury. If you use this software or hardware in dangerous applications, then you shall be responsible to take all appropriate fail-safe, backup, redundancy, and other measures to ensure its safe use. Oracle Corporation and its affiliates disclaim any liability for any damages caused by use of this software or hardware in dangerous applications.

Third-Party Content, Products, and Services Disclaimer

This software or hardware and documentation may provide access to or information on content, products, and services from third parties. Oracle Corporation and its affiliates are not responsible for and expressly disclaim all warranties of any kind with respect to third-party content, products, and services. Oracle Corporation and its affiliates will not be responsible for any loss, costs, or damages incurred due to your access to or use of third-party content, products, or services.

Alpha and Beta Draft Documentation Notice

If this document is in preproduction status:

This documentation is in preproduction status and is intended for demonstration and preliminary use only. It may not be specific to the hardware on which you are using the software. Oracle Corporation and its affiliates are not responsible for and expressly disclaim all warranties of any kind with respect to this documentation and will not be responsible for any loss, costs, or damages incurred due to the use of this documentation.