Question

我有这两张桌子：

dbo.Restaurants(rid,name,phone,area,address,zip,desc,foodtype,avgRating)

和

dbo.Reviews(rev_id,rest_id,user_id,taste, service,environment,value,average,comment)

我一直在尝试创建一个执行此操作的触发器：当dbo.Reviews上的一行被删除，更新或插入时，触发器会计算出餐厅的新平均评级，如下所示：

select rid, round(avg(average)*20,0) as 'average' 
from dbo.Restaurants inner join dbo.Reviews on rid=rest_id 
group by rid

然后在dbo.Restaurants上更新avgRating单元格，其中dbo.Restaurants.rid = dbo.Reviews.rest_id。

到目前为止，我已经想出了这个：

CREATE TRIGGER [defAverage]
ON [dbo].[Reviews]
AFTER UPDATE, DELETE, INSERT
AS
BEGIN

select rid, round(avg(average)*20,0) as 'average' 
from Restaurants inner join Reviews on rid=rest_id 
group by rid
order by 'average' desc
    SET NOCOUNT ON
    UPDATE [dbo].[Restaurants]
    SET [dbo].[Restaurants].avgRating = 'average'
    where [dbo].[Reviews].rest_id = [dbo].[Restaurants].rid

END

这显然不起作用，否则我不会在这里。我使用的是使用SQL Server Tools 2012的Visual Studio Ultimate 2013.

提前感谢您的时间和建议。

Answer 1

有两个名为inserted和deleted的伪表，仅在DML触发器中可用。由于显而易见的原因inserted表格delete为空，deleted在insert的情况下为空，在update的情况下，两个表均为空填充。你可以在触发器中使用它们。

CREATE TRIGGER [defAverage]
ON [dbo].[Reviews]
AFTER UPDATE, DELETE, INSERT
AS
BEGIN

SET NOCOUNT ON
UPDATE [dbo].[Restaurants]
    SET avgRating = round(avg(rv.average)*20,0)
from Restaurants r inner join Reviews rv on r.rid=rv.rest_id 
where r.rid in (select rest_id from inserted
                union
                select rest_id from deleted)
group by r.rid

END

触发更新另一个表的特定单元格

1 个答案: