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## ln function

The `ln` function returns the natural logarithmic value (base `e`) of the specified expression.

Syntax:

    double ln(n)

Semantics:

- n: The argument n is an expression that resolves to a number.
- return type: double.
  - Returns a NULL value in the following cases:
    - n resolves to a NULL value
    - n does not resolve to a number
  - Returns NaN in the following cases:
    - n resolves to NaN
    - n is less than zero
  - Returns positive infinity if n resolves to positive infinity.
  - Returns negative infinity if n is positive/negative zero.

Example 12-83 ln function

    SELECT ln(n) FROM PHtable

Value of n | Output
--- | ---
1 | 0.0
10 | 2.302585092994046
1.0E-7 | -16.11809565095832