--> 测试数据：[t1]
go
if object_id('[t1]') is not null 
drop table [t1]
go
create table [t1](
[ID] int,
[UserID] varchar(7),
[Score] int,
[Addtime] datetime
)
go
insert [t1]
select 1,'0815001',60,'2012-3-10' union all
select 2,'0815001',70,'2012-3-11' union all
select 3,'0815001',80,'2012-3-8' union all
select 4,'0815002',75,'2012-3-8' union all
select 5,'0815002',70,'2012-3-8' union all
select 6,'0815003',90,'2012-3-6' union all
select 7,'0815003',90,'2012-3-7'

--假如存在相同分数，我取日期较大的那个
;with t
as(
select ID,UserID,Score, Addtime from [t1] a
where Score=(select max(Score) from [t1] b where a.UserID=b.UserID)
)
select * from t a
where Addtime=(select MAX(Addtime) from t b where a.UserID=b.UserID)
--或者
select * from(
select ID,UserID,Score, Addtime from [t1] a
where Score=(select max(Score) from [t1] b where a.UserID=b.UserID))c
where c.Addtime=(select MAX(Addtime) from (select ID,UserID,Score,
 Addtime from [t1] a where Score=(select max(Score) from [t1] b 
 where a.UserID=b.UserID)
)d where c.UserID=d.UserID) order by ID

/*
ID    UserID    Score    Addtime
3    0815001    80    2012-03-08 00:00:00.000
4    0815002    75    2012-03-08 00:00:00.000
7    0815003    90    2012-03-07 00:00:00.000
*/