如何使用触发器保护表数据免受意外删除命令的影响

Question

我想创建一个触发器，它将确保除非我们不禁用触发器，否则不能从表中删除任何记录。   请把宝贵的时间用于解决这个问题。

Answer 1

您可以使用如下。只要在表上触发delete语句，此trigger就会引发错误。

SQL> CREATE OR REPLACE TRIGGER DONT_DELETE
  2       BEFORE DELETE
  3       ON TAB1
  4       FOR EACH ROW
  5  BEGIN
  6       RAISE_APPLICATION_ERROR (-20000,'No delete allowed');
  7  END;
  8  /

Trigger created.

SQL> select * from tab1;

       COL
----------
         1
         2
         3

SQL> delete from tab1 where col = 1;
delete from tab1 where col = 1
            *
ERROR at line 1:
ORA-20000: No delete allowed
ORA-06512: at "SCOTT.DONT_DELETE", line 2
ORA-04088: error during execution of trigger 'SCOTT.DONT_DELETE'