MySQL的savepoint简介及实例

生成一个savepoint：
    SAVEPOINT the_savepoint_name
回滚事务到某个savepoint：
    ROLLBACK [WORK] TO [SAVEPOINT] the_savepoint_name
释放暂存点：
	RELEASE SAVEPOINT the_savepoint_name

mysql> select * from Words where id in (1,2);
+----+------+
| id | word |
+----+------+
|  1 | aaaa |
|  2 | aaab |
+----+------+
2 rows in set (0.00 sec)

mysql> start transaction with consistent snapshot;
Query OK, 0 rows affected (0.00 sec)
mysql> update words set word=concat(word,'hi') where id=1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0
mysql> savepoint sp_id_1; // 生成第一个暂存点
Query OK, 0 rows affected (0.00 sec)
mysql> update words set word=concat(word,'hi') where id=2;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0
mysql> savepoint sp_id_2; // 生成第二个暂存点
Query OK, 0 rows affected (0.00 sec)
mysql> rollback to savepoint sp_id_1; // 回滚到第一个暂存点，则第一个暂存点之后的所有修改都会被回滚，但第一个暂存点之前的修改回被保留
Query OK, 0 rows affected (0.00 sec)
mysql> commit;
Query OK, 0 rows affected (0.06 sec)
mysql> select * from words where id in (1,2); 
+----+--------+
| id | word   |
+----+--------+
|  1 | aaaahi |
|  2 | aaab   |
+----+--------+
2 rows in set (0.00 sec)