String comparisons are not case sensitive : Not equal « Comparison Functions Operators « MySQL Tutorial

1. MySQL Tutorial
2. Comparison Functions Operators
3. Not equal

mysql>
mysql> SELECT 'AB' <> 'ab';
+--------------+
| 'AB' <> 'ab' |
+--------------+
|            0 |
+--------------+
1 row in set (0.00 sec)

mysql>
mysql> SELECT 'AB' = 'ab';
+-------------+
| 'AB' = 'ab' |
+-------------+
|           1 |
+-------------+
1 row in set (0.00 sec)

mysql>