SQL TCL语句练习

--TCL 事务控制语言
--COMMIT提交
UPDATE new_emp SET ename = 'SCOTT8888' 
WHERE empno = 7788;
COMMIT;

--ROLLBACK 回滚
UPDATE new_emp SET ename = 'ADAMS5555'
WHERE empno = 7876;
ROLLBACK;

          --SAVEPOINT
UPDATE new_emp SET ename = 'ADAMS5505'
WHERE empno = 7876;
SAVEPOINT a;
          --以上语句执行，以下语句未执行
 INSERT INTO new_emp (empno, ename, job)
 VALUES (1111, '小明', 'SALESMAN');
 ROLLBACK TO a;
 
 --锁
 --查询语句加锁
 SELECT * FROM new_emp 
 FOR UPDATE NOWAIT;
 
 --手动锁表
 --乐观锁
 LOCK TABLE new_emp IN SHARE MODE;
 --悲观锁
 LOCK TABLE new_emp IN EXCLUSIVE MODE;