sql查询视图只有列名没有数据

Question

问题遇到的现象和发生背景

列了个视图，需要查询aid和为2(选了两门课程)。但是出来的只有列名没有数据(count(aid)=2)，把2改为0数据又出来了，但不是我想要的。所以想问问大家我代码哪里打错了啊。

问题相关代码，请勿粘贴截图

create view cgs
as
select a.name as aname,a.class,c.grade,b.name as bname,a.studentid as aid,c.courseid as cid
from student as a join grade as c
on a.studentid=c.studentid
join course as b
on b.courseid=c.courseid

select aname,class,grade,bname,aid from cgs
group by aname,class,grade,bname,aid having count(aid)>2

运行结果及报错内容

我的解答思路和尝试过的方法

我想要达到的结果

Answer 1

;with t as (select aname,count() cts from cgs group by cts having count()=2)
select cgs.* from t join cgs on t.aname=ags.aname
如果要判断同一人在同一班级有2门课程的话，cte里面的分组要加上班级