PostgreSQL log() Function

The PostgreSQL log() function returns the logarithm of the specified base of the number specified by the argument.

log() Syntax

This is the syntax of the PostgreSQL log() function:

log(base, numeric_value) -> double precision

log(10, numeric_value) is equivalent to log10(numeric_value).

Parameters

base

Required. base.

numeric_value

Required. A number whose logarithm needs to be obtained.

Return value

The PostgreSQL log() function returns the logarithm of the specified base of the number specified by the argument.

The log() function will return NULL if the argument is NULL.

If the argument is zero, PostgreSQL will give an error: “Cannot take logarithm of zero”.

If the argument is negative, PostgreSQL will give an error: “Cannot take logarithm of negative number”.

PostgreSQL will give an error if you supply a parameter that is not a numeric type.

log() Examples

Here are a few examples of the log() function:

SELECT
    log(2, 3) AS "log(2, 3)",
    log(10, 4) AS "log(10, 4)";

     log(2, 3)      |     log(10, 4)
--------------------+--------------------
 1.5849625007211562 | 0.6020599913279624

log(10, numeric_value) is equivalent to log10(numeric_value). E.g:

SELECT
    log(10, 4) AS "log(10, 4)",
    log10(4) AS "log10(4)";

     log(10, 4)     |      log10(4)
--------------------+--------------------
 0.6020599913279624 | 0.6020599913279624