PostgreSQL LOG() Function

The PostgreSQL LOG() function returns the base-10 logarithm or logarithm to the specified base of a given number. In special cases it returns the following:

• If the number is less than or equal to 0, then an error is returned.
• If the base is less than or equal to 0, then an error is returned.
• If the base is equal to 1, then an error is returned.

Syntax

/* base-10 logarithm of number */
LOG(number)

/* logarithm of number to the specified base */
LOG(base, number)

Parameters

Return Value

Returns the base-10 logarithm or logarithm to the specified base of a given number.

Example 1:

The example below shows the usage of LOG() function.

SELECT LOG(1);
Result: 0

SELECT LOG(1.5);
Result: 0.1760912590556812

SELECT LOG(5);
Result: 0.6989700043360189

SELECT LOG(3, 4);
Result: 1.2618595071429149

SELECT LOG(0.7, 0.8);
Result: 0.6256216061886873

SELECT LOG(0.5, 10);
Result: -3.3219280948873623

SELECT LOG(5, 25);
Result: 2.0000000000000000

Example 2:

Consider a database table called Sample with the following records:

The statement given below can be used to calculate the base-10 logarithm of column x.

SELECT *, LOG(10, x) AS LOG_Value FROM Sample;

This will produce the result as shown below:

Example 3:

Consider a database table called Sample with the following records:

To calculate the logarithm of records of column x with base as records of column y, the following query can be used:

SELECT *, LOG(y, x) AS LOG_Value FROM Sample;

This will produce the result as shown below: