mysql>
Tests whether a value is NULL.
mysql>
mysql> SELECT 1 IS NULL, 0 IS NULL, NULL IS NULL;
+-----------+-----------+--------------+
| 1 IS NULL | 0 IS NULL | NULL IS NULL |
+-----------+-----------+--------------+
| 0 | 0 | 1 |
+-----------+-----------+--------------+
1 row in set (0.00 sec)
mysql>