(root@localhost) [test]> create temporary table t (name varchar(10));
Query OK, 0 rows affected (0.00 sec)
(root@localhost) [test]> insert into t values (''),(\N);
Query OK, 2 rows affected (0.00 sec)
Records: 2 Duplicates: 0 Warnings: 0
(root@localhost) [test]> select * from t;
+------+
| name |
+------+
| |
| NULL |
+------+
2 rows in set (0.01 sec)
(root@localhost) [test]> select * from t where name is null;
+------+
| name |
+------+
| NULL |
+------+
1 row in set (0.00 sec)
(root@localhost) [test]> select * from t where name is not null;
+------+
| name |
+------+
| |
+------+
1 row in set (0.00 sec)