在Update语句中使用子查询

Question

我在删除时触发的触发器中有以下 SQL 语句：

UPDATE bk2_InfoPages
SET SortOrder = SortOrder - (SELECT COUNT(*) FROM Deleted d WHERE d.SortOrder <= SortOrder)

我的问题是最后一个

SortOrder

指的是

Deleted

表而不是

bk2_InfoPages

表。我不允许向

bk2_InfoPages

表添加别名，因为它是

UPDATE

语句 - 那么我应该做什么呢？

Answer 1

UPDATE bk2_InfoPages
SET SortOrder = SortOrder - (SELECT COUNT(*) FROM Deleted d WHERE d.SortOrder <= bk2_InfoPages.SortOrder)

Answer 2

这应该有效：

UPDATE b
SET SortOrder = SortOrder - 
  (SELECT COUNT(*) FROM Deleted d WHERE d.SortOrder <= b.SortOrder)
from bk2_InfoPages b

你必须给你的表起别名才能做子查询，例如：

-- this executes fine 
create table #t ( t int)

update t 
set t = (select count(*) from #t t1 where t.t = t1.t)
from #t t

Answer 3

希望这会起作用！

UPDATE bk2_InfoPages
SET SortOrder = SortOrder - subquery.c
FROM (
SELECT SortOrder, COUNT(*) AS c
FROM Deleted d
GROUP BY SortOrder
) AS subquery
WHERE subquery.SortOrder <= bk2_InfoPages.SortOrder;