LOG

Calculate logarithm. This function returns the natural logarithm of a number, or the logarithm to a specified base if two arguments are provided.

Syntax

LOG(X), LOG(B,X)

Description

If called with one parameter, this function returns the natural logarithm of X. If X is less than or equal to 0, then NULL is returned.

If called with two parameters, it returns the logarithm of X to the base B. If B is <= 1 or X <= 0, the function returns NULL.

If any argument is NULL, the function returns NULL.

The inverse of this function (when called with a single argument) is the EXP() function.

Examples

LOG(X):

SELECT LOG(2);
+-------------------+
| LOG(2)            |
+-------------------+
| 0.693147180559945 |
+-------------------+

SELECT LOG(-2);
+---------+
| LOG(-2) |
+---------+
|    NULL |
+---------+

LOG(B,X)

SELECT LOG(2,16);
+-----------+
| LOG(2,16) |
+-----------+
|         4 |
+-----------+

SELECT LOG(3,27);
+-----------+
| LOG(3,27) |
+-----------+
|         3 |
+-----------+

SELECT LOG(3,1);
+----------+
| LOG(3,1) |
+----------+
|        0 |
+----------+

SELECT LOG(3,0);
+----------+
| LOG(3,0) |
+----------+
|     NULL |
+----------+

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