oracle学习9

一、事务

 

从一种状态到另一种状态：

比如转账：一个人的钱多了或者少了

1.COMMIT 

2.ROLLBACK 

3.SAVEPOINT 

 

SELECT * from ms_brda1
（1）select count(*) from ms_brda1

（2）delete from ms_brda1 where brid=158475
select count(*) from ms_brda1

（3）savepoint a;
select count(*) from ms_brda1

（4）delete from ms_brda1 where brid=158477
select count(*) from ms_brda1
(5)savepoint b;

(6)rollback to savepoint a;

(7)rollback to savepoint b; 

(8)rollback ;

（1）

 

（2）

（3）savepoint a;

（4）

（5）savepoint b;

(6)rollback to savepoint a;

 

(7)rollback to savepoint b; 

上面的情况是因为没分清楚先后顺序

先设置的“保存点A”，然后设置的“保存点B”

你已经回滚到A了，已经越过B了，再想回到B是不可以的

但是可以先回到B再回到A，

(8)rollback ;

而rollback是回到最初的状态

即

这样是因为deleted与select需要手动commit

所以可以rollback到最初的状态