oracle 事务 - 度量快速开发平台-专业、快速的软件定制快开平台

五、事务的几个重要操作
1.设置保存点 savepoint a
2.取消部分事务 rollback to a
3.取消全部事务 rollback
eg、
SQL> savepoint a; --创建保存点a
Savepoint created

SQL> delete from emp where empno=7782;
1 row deleted

SQL> savepoint b; --创建保存到b
Savepoint created

SQL> delete from emp where empno=7934;
1 row deleted

SQL> select * from emp where empno=7934; --无法查询到empno为7934这条记录，因为这条记录已被删除
EMPNO ENAME    JOB       MGR HIREDATE       SAL    COMM DEPTNO
----- ---------- --------- ----- ----------- --------- --------- ------

SQL> rollback to b; --通过保持点来恢复这条记录
Rollback complete

SQL> select * from emp where empno=7934;
EMPNO ENAME    JOB       MGR HIREDATE       SAL    COMM DEPTNO
----- ---------- --------- ----- ----------- --------- --------- ------
7934 MILLER    CLERK    7782 1982/1/23    1300.00             10

SQL> select * from emp where empno=7782; --无法查询到empno为7982这条记录，因为这条记录已被删除
EMPNO ENAME    JOB       MGR HIREDATE       SAL    COMM DEPTNO
----- ---------- --------- ----- ----------- --------- --------- ------

SQL> rollback to a; --通过保持点来恢复这条记录
Rollback complete

SQL> select * from emp where empno=7782;
EMPNO ENAME    JOB       MGR HIREDATE       SAL    COMM DEPTNO
----- ---------- --------- ----- ----------- --------- --------- ------
7782 CLARK    MANAGER 7839 1981/6/9    2450.00             10

SQL>
注意：这个回滚事务，必须是没有commit前使用的；如果事务提交了，那么无论你刚才做了多少个保存点，都统统没用。如果没有手动执行commit,而是exit了，那么会自动提交。
eg、
SQL> savepoint a;
Savepoint created

SQL> delete from emp where empno=7782;
1 row deleted

SQL> commit;
Commit complete

SQL> rollback to a;
rollback to a
ORA-01086: 从未创建保存点 'A'
SQL>