mysql>
mysql> SELECT LOG(2);
+------------------+
| LOG(2) |
+------------------+
| 0.69314718055995 |
+------------------+
1 row in set (0.00 sec)
mysql>
mysql> SELECT LOG(-2);
+---------+
| LOG(-2) |
+---------+
| NULL |
+---------+
1 row in set (0.00 sec)
mysql>