mysql> SELECT LENGTH('test') != CHAR_LENGTH('test');
+---------------------------------------+
| LENGTH('test') != CHAR_LENGTH('test') |
+---------------------------------------+
|                                     0 |
+---------------------------------------+
1 row in set (0.05 sec)

mysql> SELECT LENGTH('test') != CHAR_LENGTH ('test');
ERROR 1305 (42000): FUNCTION test.CHAR_LENGTH does not exist