I can't change the case of a column with a unique index, example below. MariaDB [test]> show columns in kae; +-------+---------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------+---------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | name | varchar(2048) | NO | UNI | NULL | | +-------+---------------+------+-----+---------+----------------+ 2 rows in set (0.001 sec) MariaDB [test]> select * from kae; +----+------+ | id | name | +----+------+ | 1 | test | +----+------+ 1 row in set (0.001 sec) MariaDB [test]> update kae set name="Test" where id=1; ERROR 1062 (23000): Duplicate entry 'Test' for key 'unique_name' MariaDB [test]>