How the Ln() Function Works in PostgreSQL

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In PostgreSQL, ln() is a mathematical function that returns the natural logarithm of its argument.

Syntax

The official syntax goes like this:

ln(dp or numeric)

Where dp is a double precision value.

Example

Here’s an example of how it works.

SELECT ln(10);

Result:

2.302585092994046

Fractions

This example includes a fractional part in the argument.

SELECT ln(32.53);

Result:

3.4821627404852601

Expressions

You can include expressions, such as this.

SELECT ln(12 * 2);

Result:

3.1780538303479458

Ln() vs Exp()

The ln() function returns the natural logarithm, which is the inverse of exp(), which returns the exponential value of its argument.

The exponential of the natural logarithm of a number is the number itself.

And the natural logarithm of the exponential of a number is the number itself.

Here’s an example that verifies this.

SELECT 
  ln(exp(1)),
  exp(ln(1));

Result:

 ln | exp
----+-----
  1 | 1