--是要删除表中多余的数据，保留每个用户最新的两条的数据吗？如：
delete UserLogin from UserLogin a
where (select count(distinct logintime) from userlogin where userid=a.userid and logintime>=a.logintime)>2

--如果是查询最新的2条，不改变原始数据
select * from UserLogin a
where (select count(distinct logintime) from userlogin where userid=a.userid and logintime>=a.logintime)<=2

------解决方案--------------------
对userid分组，使用row_number()over()排序 取<3就行。

------解决方案--------------------
建立插入触发器在触发器中引用一楼的删除语句：
 delete UserLogin from UserLogin a
where a.userid=(select userid from inserted) and logintime not in (select top 2 logintime from userlogin where userid=(select userid from inserted) order by logintime)

------解决方案--------------------
此问题有点类似：http://www.dbfaq.net/FAQ/NewQL.aspx?QuestionID=71请参考

------解决方案--------------------
表记录的重复数据删除：
http://www.dbfaq.net/FAQ/FixupQL.aspx?QuestionID=30


------解决方案--------------------

; with cte ( select row_number() over( paritition by userid order by userid, logintime desc ) as xh ,* from UserLogin )  

delete from cte where xh >=3

------解决方案--------------------
探讨

; with cte ( select row_number() over( paritition by userid order by userid, logintime desc ) as xh ,* from UserLogin ) 

delete from cte where xh >=3