Syntax
LOG([B,]X)
Purpose
You can call LOG(X) to return the natural logarithm of X, which is the base-e logarithm of X. If X is less than or equal to 0, the function returns NULL and reports the alert Invalid argument for logarithm. If only X is provided, this function is equivalent to LN(X).
You can call LOG(B,X) to return the logarithm of X to base B. If X is less than or equal to 0, or B is less than or equal to 1, the function returns NULL.
Examples
obclient> SELECT LOG(-10), LOG(0), LOG(10), LOG(-3.14), LOG(3.14);
+----------+--------+-------------------+------------+-------------------+
LOG(-10) LOG(0) LOG(10) LOG(-3.14) LOG(3.14)
+----------+--------+-------------------+------------+-------------------+
NULL NULL 2.302585092994046 NULL 1.144222799920162
+----------+--------+-------------------+------------+-------------------+
1 row in set, 3 warnings (0.00 sec)
obclient> SELECT LOG(10, 100), LOG(1,100);
+--------------+------------+
LOG(10, 100) LOG(1,100)
+--------------+------------+
2 NULL
+--------------+------------+
1 row in set, 1 warning (0.00 sec)
