Data truncated for column......

mysql> select database() as db_name;
+---------+
| db_name |
+---------+
| test |
+---------+
1 row in set (0.00 sec)
mysql> insert intoclassmate(
-> sex
-> )
-> values (
-> 'boy'
-> );
ERROR 1265 (01000): Data truncated for column 'sex' at row 1
mysql> insert intotest.classmate(
-> sex
-> )
-> values
-> (
-> 'boy'
-> );
Query OK, 1 row affected (0.04 sec)

注:
     db: test
    tbl: classmate
请各位给予指教，在此先谢过了！