sql - 防止某些行在 Oracle 中被删除

Question

我想用 VERSIONID=1 阻止任何行在某个表中被删除。我还想将其记录在审计表中，以便我们可以查看何时发生这种情况以进行记录。我试图用触发器来做到这一点:

CREATE TRIGGER TPMDBO.PreventVersionDelete
  BEFORE DELETE ON TPM_PROJECTVERSION
  FOR EACH ROW
DECLARE
BEGIN
  IF( :old.VERSIONID = 1 )
  THEN
    INSERT INTO TPM_AUDIT VALUES ('Query has attempted to delete root project version!', sysdate);
    RAISE_APPLICATION_ERROR( -20001, 'Query has attempted to delete root project version!' );
  END IF;
END;

我得到以下结果:

SQL> delete from TPM_PROJECTVERSION where PROJECTID=70 and VERSIONID=1;
delete from TPM_PROJECTVERSION where PROJECTID=70 and VERSIONID=1
            *
ERROR at line 1:
ORA-20001: Query has attempted to delete root project version!
ORA-06512: at "TPMDBO.PREVENTVERSIONDELETE", line 6
ORA-04088: error during execution of trigger 'TPMDBO.PREVENTVERSIONDELETE'

然而，表TPM_AUDIT是空的。难道我做错了什么？

Answer 1

如果您的触发器引发错误，DELETE语句失败，事务将回滚到运行语句之前创建的隐式保存点。这意味着触发器所做的任何更改也会回滚。

您可以通过使用自治事务来解决此问题。就像是

CREATE PROCEDURE write_audit
AS
  PRAGMA AUTOMOMOUS_TRANSACTION;
BEGIN
  INSERT INTO tpm_audit
    VALUES( 'Query has attempted to delete root project version!',
            sysdate );
  commit;
END;

CREATE TRIGGER TPMDBO.PreventVersionDelete
  BEFORE DELETE ON TPM_PROJECTVERSION
  FOR EACH ROW
DECLARE
BEGIN
  IF( :old.VERSIONID = 1 )
  THEN
    write_audit;
    RAISE_APPLICATION_ERROR( -20001, 'Query has attempted to delete root project version!' );
  END IF;
END;

这将把 INSERT进入 TPM_AUDIT到可以在 DELETE 的上下文之外提交的单独事务中陈述。使用自治事务时要非常小心，但是

如果您发现自己将自治事务用于写入日志表以外的任何事情，那么您几乎肯定做错了。

使用自治事务声明的 PL/SQL 块中的代码是真正自治的，因此它看不到当前 session 所做的未提交更改。

因为写一致性，Oracle 完全有可能会部分执行一个 DELETE语句，多次触发行级触发器，回滚该工作，然后重新执行 DELETE .但是，这种静默回滚不会回滚自治事务所做的更改。所以完全有可能是单个DELETE单行实际上会导致触发器被触发多次，因此，在 TPM_AUDIT 中创建多行.