当我添加key列时，这个查询给了我一个错误，有什么帮助吗？
username和product是复合主键，以防万一。
mysql> select * from sw_product_session where username='admin';
+----------+----------+------------+----------------------------+
| username | product | expire | key |
+----------+----------+------------+----------------------------+
| admin | printbox | 1373550885 | 2ijm77cpnfc7miktasopkik2q2 |
+----------+----------+------------+----------------------------+
1 row in set (0.00 sec)
mysql> select * from sw_product_session where username='admin' AND product='printbox';
+----------+----------+------------+----------------------------+
| username | product | expire | key |
+----------+----------+------------+----------------------------+
| admin | printbox | 1373550885 | 2ijm77cpnfc7miktasopkik2q2 |
+----------+----------+------------+----------------------------+
1 row in set (0.00 sec)
mysql> select * from sw_product_session where username='admin' AND product='printbox' AND key='2ijm77cpnfc7miktasopkik2q2';
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'key='2ijm77cpnfc7miktasopkik2q2'' at line 1
您需要记住，任何保留字都需要转义：
AND `key`='...'