触发以防止从表中删除任何内容答案

【问题标题】：Trigger to prevent Any Deleting from Table触发以防止从表中删除任何内容
【发布时间】：2017-06-17 07:50:01
【问题描述】：

这个新的租赁历史表的触发器，防止从表中删除。

CREATE OR REPLACE  TRIGGER RENTALHIS_DEL
BEFORE DELETE ON RENTALHISTORY
BEGIN
dbms_output.put_line( 'Records can not be deleted');
END;

DELETE FROM RENTALHISTORY WHERE RENTALID = 1;



-- It is deleting before it says it can not delete

1 rows deleted.

Records can not be deleted

【问题讨论】：

添加到触发器正文中：raise_application_error(-20001,'Records can not be deleted');
看到这个已经回答了：stackoverflow.com/a/16449271/460557

标签： sql oracle triggers

【解决方案1】：

dbms_output.put_line( 'Records can not be deleted');

上面只是打印文本和触发器成功完成，然后删除无论如何都会发生。您想要做的是引发错误以阻止程序完成。

使用标准程序raise_application_error 停止程序并引发错误：

CREATE OR REPLACE  TRIGGER RENTALHIS_DEL
BEFORE DELETE ON RENTALHISTORY
BEGIN
    raise_application_error(-20001,'Records can not be deleted');
END;
/

【讨论】：

【解决方案2】：

您想引发错误，而不是打印消息。无论如何都会删除：

CREATE OR REPLACE  TRIGGER RENTALHIS_DEL
BEFORE DELETE ON RENTALHISTORY
BEGIN
  RAISE_APPLICATION_ERROR (-20000, 'Deletion not supported on this table');
END;

或者，您可以使用instead of 触发器来防止发生删除：

CREATE OR REPLACE TRIGGER RENTALHIS_DEL
INSTEAD OF DELETE ON RENTALHISTORY
BEGIN
   dbms_output.put_line( 'Records cannot be deleted');
END;

【讨论】：

【解决方案3】：

之后您可以使用commit after your delete statement and rollback 使用Pragma 到达上一阶段。

     CREATE OR REPLACE  TRIGGER 
     RENTALHIS_DEL
    AFTER DELETE ON RENTALHISTORY
       DECLARE
       PRAGMA 
          AUTONOMOUS_TRANSACTION;
      BEGIN
      RAISE_APPLICATION_ERROR 
     (-20000, 'Deletion getting rolled 
     back');
           ROLLBACK;
             END;

【讨论】：