回滚到SAVEPOINT

Question

我在phpmyadmin中尝试以下语句。数据库：mysql。

INSERT into cust values(5,'srk'); 
commit; 
UPDATE cust set cname='sk' where cid=5; 
savepoint A;

这些陈述成功执行。

但是当我执行

时

rollback to A;

错误：

  

#1305 - SAVEPOINT A does not exist

错误即将来临。

如果我只执行回滚; 它成功执行但实际上没有回滚结果。

Answer 1

首先，你甚至没有参与交易。甚至一次为rollback to a savepoint，你必须承诺让它被看到。你只需要玩它。这应该对我有所帮助。

使用start transaction;

启动交易

create table cust
(   id int auto_increment primary key,
    theValue int not null,
    theText varchar(50) not null,
    cname varchar(50) not null,
    cid int not null
);

INSERT into cust (theValue,theText,cname,cid) values(111,'aaa','a',1); 


start transaction;
    savepoint B1;
    INSERT into cust (theValue,theText,cname,cid) values(666,'aaa','a',1); 
    savepoint B2;
    INSERT into cust (theValue,theText,cname,cid) values(777,'aaa','a',1); 
    ROLLBACK to B2;
    -- at this moment, this connection can see 2 rows, other connections see 1 (id=1)
    select * from cust; -- visible to you but not others, that is,
commit;
-- at this moment all connections can see 2 rows. Give it a try with another connection open

select * from cust;
+----+----------+---------+-------+-----+
| id | theValue | theText | cname | cid |
+----+----------+---------+-------+-----+
|  1 |      111 | aaa     | a     |   1 |
|  2 |      666 | aaa     | a     |   1 |
+----+----------+---------+-------+-----+

从手册页SAVEPOINT, ROLLBACK TO SAVEPOINT, and RELEASE SAVEPOINT Syntax

  

ROLLBACK TO SAVEPOINT语句将事务回滚到   命名保存点而不终止事务。

重要的是要知道，在代码第2行commit中，您从未进行过交易。你从未开始过。 commit没有任何内容。

第1行，插入，考虑到它不在事务中，是一个迷你隐式事务。它刚刚发生。当第2行出现时，服务器正在思考，提交什么？

Answer 2

您必须设置，

set autocommit = 0;