高手请指点 多表联合分组查询解决方案

高手请指点 多表联合分组查询
我想通过三个表联事查询并按姓名进行分组
这是下面的代码
select   C1.UserName   as   姓名,C.ID   as   计算机名,R.fee   as   总费用
from   Record   as   R
inner   join   Card   as   C1   on(C1.ID=R.Cardid)
inner   join   Computer   as   C   on(C.ID=R.ComputerID)
WHERE   datepart(week,R.ENDTIME)=DATEPART(WEEK,getdate())
group   by   C1.UserName

错误提示是：
服务器:   消息   8120，级别   16，状态   1，行   1
列   'C.ID '   在选择列表中无效，因为该列既不包含在聚合函数中，也不包含在   GROUP   BY   子句中。
服务器:   消息   8120，级别   16，状态   1，行   1
列   'R.Fee '   在选择列表中无效，因为该列既不包含在聚合函数中，也不包含在   GROUP   BY   子句中。

------解决方案--------------------
select
C1.UserName as 姓名,
C.ID as 计算机名,
SUM(R.fee) as 总费用
from
Record as R
inner join
Card as C1
on
C1.ID=R.Cardid
inner join
Computer as C
on
C.ID=R.ComputerID
WHERE
datepart(week,R.ENDTIME)=DATEPART(WEEK,getdate())
group by
C1.UserName,C.ID
------解决方案--------------------
或者你這麼寫吧


select C1.UserName as 姓名,Min(C.ID) as 计算机名,SUM(R.fee) as 总费用
from Record as R
inner join Card as C1 on(C1.ID=R.Cardid)
inner join Computer as C on(C.ID=R.ComputerID)
WHERE datepart(week,R.ENDTIME)=DATEPART(WEEK,getdate())
group by C1.UserName