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## Using Left Outer joins with parent-child tables

A JOIN is used to combine rows from two or more tables, based on a related column between them. In a hierarchical table, the child table inherits the primary key columns of its parent table. This is done implicitly, without including the parent columns in the `CREATE TABLE` statement of the child. All tables in the hierarchy have the same shard key columns.

A Left Outer Join (LOJ) is one of the join operations that allows you to specify a join clause.

- Overview of Left Outer Joins
- Examples using Left Outer Joins