求助：SQL Server语句出错求改正！！

我写了一个SQL Server语句，内容如下：

 select C.courseID,C.courseName,C.teacherID,C.teacherName,Sum(e.Grade) As count 
from EvaluateTeacherGrade e,Course C,Grade G where e.courseID=G.courseID and C.courseID=G.courseID and G.studentID='0711001'and C.courseID='100000'

但是有提示错误：
消息 8120，级别 16，状态 1，第 1 行
选择列表中的列 'Course.courseID' 无效，因为该列没有包含在聚合函数或 GROUP BY 子句中。
我该如何改正啊？？

   SELECT C.COURSEID,
          C.COURSENAME, 
                    C.TEACHERID,
                    C.TEACHERNAME,
                    SUM(E.GRADE) AS COUNT 
     FROM EVALUATETEACHERGRADE E,
              COURSE C,
                    GRADE G 
    WHERE E.COURSEID=G.COURSEID    
          AND C.COURSEID=G.COURSEID 
            AND G.STUDENTID='0711001'
            AND C.COURSEID='100000'
 GROUP BY C.COURSEID,
          C.COURSENAME, 
                    C.TEACHERID,
                    C.TEACHERNAME 

Course.courseID
->
Max(Course.courseID)
放在聚合函数中

用left join吧