mysql> CREATE TABLE ox(

    -> ok char(1) CHECK (ok in('o', 'x'))

    -> );

Query OK, 0 rows affected (0.06 sec)


mysql> insert into ox (ok)values('s');

Query OK, 1 row affected (0.00 sec)


mysql> select * from ox;

+------+

| ok   |

+------+

| s    |

+------+







o,x만 들어가게 제약조건 걸엇는데 s넣으니깐 아무 에러없이 들어가는데 뭐임 ;;