增加一列：
mysql> ALTER TABLE orderitems ADD f_id INT;
Query OK, 16 rows affected (0.04 sec)
Records: 16 Duplicates: 0 Warnings: 0
添加值：
mysql> UPDATE orderitems SET f_id=100 WHERE o_num=10001;
Query OK, 1 row affected (0.28 sec)
Rows matched: 1 Changed: 1 Warnings: 0