Question

我有一张桌子，这张桌子最多必须有1000行。当用户想要添加第1001行时，必定存在错误。我知道我应该使用插入触发器。我是SQL的新人你能帮助我吗？

我的代码是：

create or replace trigger update_ext_app_serv
before update on EXTERNAL_APP_SERVICE
for each row

declare
  row_count number;
  old_service_id number;
  new_service_trigger varchar(30);
  old_service_trigger varchar(30);
begin
  row_count := 0;
  new_service_trigger := :NEW.TRIGGER_NAME;
  old_service_trigger := :OLD.TRIGGER_NAME;
  old_service_id := :OLD.SERVICE_ID;

  select count(*) into row_count 
  from EXTERNAL_APP_PROFILE 
  where ORIG_ID = old_service_id 
  or TERM_FAILURE_RESP_ID = old_service_id 
  or TERM_ID = old_service_id;

  if (row_count > 0) and (new_service_trigger not like old_service_trigger) 
  then
      raise_application_error(-20706, 'Unable to update Trigger. The service is referenced at least External Application Profile.');
  end if;
end;

Answer 1

执行此操作的方法是使用AFTER触发器，并在语句而不是行级别。

SQL> create or replace trigger t1000_trg
  2  after insert on t1000
  3  declare
  4      n pls_integer;
  5  begin
  6      select count(*) into n
  7      from t1000;
  8      if n > 1000 then
  9          raise_application_error(-20999, 'No more than 1000 records!');
 10      end if;
 11  end;
 12  /

Trigger created.
SQL>

这是我们的测试数据。

SQL> select count(*) from t1000;

  COUNT(*)
----------
       999

SQL>

第1000条记录好......

SQL> insert into t1000 values (1000);

1 row created.

SQL>

...但是第1001条记录被拒绝了：

SQL> insert into t1000 values (1001);
insert into t1000 values (1001)
            *
ERROR at line 1:
ORA-20999: No more than 1000 records!
ORA-06512: at "FOX.T1000_TRG", line 7
ORA-04088: error during execution of trigger 'FOX.T1000_TRG'

SQL>

也适用于多行插入语句。

SQL> roll
Rollback complete.
SQL> select count(*) from t1000;

  COUNT(*)
----------
       999

SQL> insert into t1000 select 1000 + level from dual connect by level <= 5;
insert into t1000 select 1000 + level from dual connect by level <= 5
            *
ERROR at line 1:
ORA-20999: No more than 1000 records!
ORA-06512: at "FOX.T1000_TRG", line 7
ORA-04088: error during execution of trigger 'FOX.T1000_TRG'


SQL>

如何在更新触发器之前更改为插入触发器之前？

1 个答案: