大虾帮忙解释下sqlserver top 1 语句为什么取到的不是第一条记录

[bestleo55]

select top 3 uid from dbo.Account order by uid desc 显示结果为
uid
3
2
1
select top 1 uid from dbo.Account where uid in (select top 3 uid from dbo.Account order by uid desc)
取到的uid是1

select top 2 uid from dbo.Account where uid in (select top 3 uid from dbo.Account order by uid desc)
取到的uid是 3 2

top 1 应该是取第一条记录 uid应该是3的 为什么取到是1？

[youcity]

select top 1 uid from dbo.Account where uid in (select top 3 uid from dbo.Account order by uid desc) order by uid desc

in条件检索出来的结果是3 2 1 ，但这里只是作为了条件，而你主SELECT文里没有进行排序的话，每次取出来的结果可能就是从符合结果的条件里随机取得

[zhj92lxs]

[Quote=引用 1 楼 youcity 的回复:]
select  top 1 uid  from dbo.Account where uid in (select top 3 uid from dbo.Account order by uid desc) order by uid desc

in条件检索出来的结果是3 2 1 ，但这里只是作为了条件，而你主SELECT文里没有进行排序的话，每次取出来的结果可能就是从符合结果的条件里随机取得

[/Quote]
正解，不过最好不要用in