現在來解釋下：

start transaction;
就是開始事務追蹤的命令
開始前一定記得寫

然后

commit;
這個的意思是說確認提交，執行這個命令就不能rollback了，相當于執行完畢。

最后

rollback;
這個命令很簡單，回滾到start transaction時候的狀態

現在舉例
mysql> select * from useraccount ;
+-----------+--------+-------------+
| AccountID | userID | AccountName |
+-----------+--------+-------------+
| 1 | 2 | zhifubao |
+-----------+--------+-------------+
1 row in set (0.00 sec)

mysql> start transaction;
Query OK, 0 rows affected (0.00 sec)

mysql> update useraccount set userID = 1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0

mysql> select * from useraccount;
+-----------+--------+-------------+
| AccountID | userID | AccountName |
+-----------+--------+-------------+
| 1 | 1 | zhifubao |
+-----------+--------+-------------+
1 row in set (0.00 sec)

mysql> rollback; (這里假如不想回滾就用commit;就可以完成了）
Query OK, 0 rows affected (0.28 sec)

mysql> select * from useraccount;
+-----------+--------+-------------+
| AccountID | userID | AccountName |
+-----------+--------+-------------+
| 1 | 2 | zhifubao |
+-----------+--------+-------------+
1 row in set (0.00 sec)