LOG10(X) returns the base-10 logarithm of X. : LOG10 « Math Numeric Functions « MySQL Tutorial

1. MySQL Tutorial
2. Math Numeric Functions
3. LOG10

mysql>
mysql> SELECT LOG10(2);
+------------------+
| LOG10(2)         |
+------------------+
| 0.30102999566398 |
+------------------+
1 row in set (0.00 sec)

mysql>
mysql> SELECT LOG10(100);
+------------+
| LOG10(100) |
+------------+
|          2 |
+------------+
1 row in set (0.00 sec)

mysql>
mysql> SELECT LOG10(-100);
+-------------+
| LOG10(-100) |
+-------------+
|        NULL |
+-------------+
1 row in set (0.01 sec)

mysql>
LOG10(X) is equivalent to LOG(10,X).
mysql>