Question

我正在使用sql-server。我有一个类似

的表

StudentName   Class  score
Jim            a1     80
Ann            a1     83
Bill           a2     90

我想选择分数高于他/她班级平均分的学生。这是我的代码：

Select a.StudentName
From Table a
inner Join Table b
On a.class=b.class 
where a.score>(select avg(b.score) From b
group by class);

内连接方法对我来说很奇怪。请问它是否正确？有没有更好的方法来实现这一目标？

Answer 1

您已经关闭，但您可以限制子查询并取消加入：

Select a.StudentName
From Table a
where a.score > (
    select avg(b.score) score 
    From Table b
    where b.class = a.class);

Answer 2

怎么样：

;with ClassAverages as (
  select Class, AVG(score) as AVGScore FROM Table GROUP BY Class
)
SELECT StudentName FROM Table student
INNER JOIN ClassAverages ON ClassAverages.Class=student.Class
WHERE student.score>ClassAverages.AVGScore

内连接VS一些其他方法

2 个答案: