SAVEPOINT 语句可以在事务过程中标记一个“保存点”，事务可以选择回滚到这个点。保存点是可选的，一个事务过程中也可以有多个保存点。

示例：将一个事务回滚到一个保存点

下面示例展示了一个事务中包含多个 DML 语句和多个保存点，然后回滚到其中一个保存点，只丢弃了保存点后面的那部份修改。

  • 查看表当前记录
  1. obclient> select * from t_insert;
  2. +----+------+-------+---------------------+
  3. | id | name | value | gmt_create          |
  4. +----+------+-------+---------------------+
  5. |  1 | CN   | 10001 | 2020-04-03 16:05:45 |
  6. |  2 | US   | 10002 | 2020-04-03 16:05:54 |
  7. |  3 | UK   | 10003 | 2020-04-03 16:05:54 |
  8. |  4 | JP   |  NULL | 2020-04-03 16:16:46 |
  9. |  5 | DE   |  NULL | 2020-04-03 16:16:46 |
  10. +----+------+-------+---------------------+
  11. 5 rows in set (0.00 sec)
  • 开启一个事务，设置多个保存点信息。
  1. obclient> set session autocommit=off;
  2. Query OK, 0 rows affected (0.00 sec)
  4. obclient> insert into t_insert(id, name) values(6,'FR');
  5. Query OK, 1 row affected (0.00 sec)
  7. obclient> savepoint fr;
  8. Query OK, 0 rows affected (0.00 sec)
  10. obclient> insert into t_insert(id, name) values(7,'RU');
  11. Query OK, 1 row affected (0.00 sec)
  13. obclient> savepoint ru;
  14. Query OK, 0 rows affected (0.00 sec)
  16. obclient> insert into t_insert(id, name) values(8,'CA');
  17. Query OK, 1 row affected (0.00 sec)
  19. obclient> savepoint ca;
  20. Query OK, 0 rows affected (0.00 sec)
  • 当前会话能看到事务未提交的所有修改。
  1. obclient> select * from t_insert;
  2. +----+------+-------+---------------------+
  3. | id | name | value | gmt_create          |
  4. +----+------+-------+---------------------+
  5. |  1 | CN   | 10001 | 2020-04-03 16:05:45 |
  6. |  2 | US   | 10002 | 2020-04-03 16:05:54 |
  7. |  3 | UK   | 10003 | 2020-04-03 16:05:54 |
  8. |  4 | JP   |  NULL | 2020-04-03 16:16:46 |
  9. |  5 | DE   |  NULL | 2020-04-03 16:16:46 |
  10. |  6 | FR   |  NULL | 2020-04-03 16:26:22 |
  11. |  7 | RU   |  NULL | 2020-04-03 16:26:32 |
  12. |  8 | CA   |  NULL | 2020-04-03 16:26:42 |
  13. +----+------+-------+---------------------+
  14. 8 rows in set (0.00 sec)
  • 回滚事务到其中一个保存点。
  1. obclient> rollback to savepoint ru;
  2. Query OK, 0 rows affected (0.00 sec)
  4. obclient> select * from t_insert;
  5. +----+------+-------+---------------------+
  6. | id | name | value | gmt_create          |
  7. +----+------+-------+---------------------+
  8. |  1 | CN   | 10001 | 2020-04-03 16:05:45 |
  9. |  2 | US   | 10002 | 2020-04-03 16:05:54 |
  10. |  3 | UK   | 10003 | 2020-04-03 16:05:54 |
  11. |  4 | JP   |  NULL | 2020-04-03 16:16:46 |
  12. |  5 | DE   |  NULL | 2020-04-03 16:16:46 |
  13. |  6 | FR   |  NULL | 2020-04-03 16:26:22 |
  14. |  7 | RU   |  NULL | 2020-04-03 16:26:32 |
  15. +----+------+-------+---------------------+
  16. 7 rows in set (0.01 sec)
  • 提交事务，确认表最新修改包含保存点之前的修改。
  1. obclient> commit;
  2. Query OK, 0 rows affected (0.00 sec)
  3. obclient> select * from t_insert;
  4. +----+------+-------+---------------------+
  5. | id | name | value | gmt_create          |
  6. +----+------+-------+---------------------+
  7. |  1 | CN   | 10001 | 2020-04-03 16:05:45 |
  8. |  2 | US   | 10002 | 2020-04-03 16:05:54 |
  9. |  3 | UK   | 10003 | 2020-04-03 16:05:54 |
  10. |  4 | JP   |  NULL | 2020-04-03 16:16:46 |
  11. |  5 | DE   |  NULL | 2020-04-03 16:16:46 |
  12. |  6 | FR   |  NULL | 2020-04-03 16:26:22 |
  13. |  7 | RU   |  NULL | 2020-04-03 16:26:32 |
  14. +----+------+-------+---------------------+
  15. 7 rows in set (0.00 sec)
  17. obclient>