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引用了Deleted表而不是bk2_InfoPages表。我不允许在bk2_InfoPages表中添加别名，因为它是UPDATE语句 - 所以我该怎么做呢？

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

您必须对表进行别名以执行子查询，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