Question

我需要创建一种类型的触发器，当我的signedUp表中的相关记录都将被查看的字段设置为1时，将从我的事件表中删除事件记录。

   events
   ----------
   eventID
   eventName
   eventLocation    

   signedUp
   ----------
   signedID
   eventID
   empID
   viewed

查看字段默认为0，但当用户查看与事件有关的消息时，将其设置为1，一旦所有用户查看了该消息，他们的所有标志都将设置为1，此时我想要从事件表中删除相关记录，如何创建触发器来执行此操作？

Answer 1

Create TRIGGER [dbo].[<tr_name>]
   ON [dbo].[signedUp]
   AFTER UPDATE
AS 
BEGIN
SET NOCOUNT ON;

if exists(select s.eventID from signedUp s 
inner join inserted i on i.eventid = s.eventid
group by s.eventID
having count(s.eventID) = SUM(s.viewed))
delete e from events e inner join inserted i on i.eventid = e.eventid
END

Answer 2

试试这个：

CREATE OR REPLACE TRIGGER signedup_sau -- statement after update
AFTER UPDATE ON signedup
    DELETE FROM events
    WHERE NOT EXISTS (SELECT 1
                        FROM signedup
                       WHERE signedup.eventid = events.eventid
                         AND signedup.viewed != 1);
END;

触发器必须在整个UPDATE语句运行后运行，因为在行级触发器中引用同一个表既不可能也不合理。

根据另一个表中的列值从一个表中删除记录

2 个答案: