我的学生数据库跟你的差不多,我就用我的这些表给你做了个
select c.Cno,s.Sname,s.Sno,选课人数 from Course c
left join SC on c.cno=sc.cno
left join student s on s.Sno=SC.Sno
left join (select c.cno, COUNT(s.Sno) 选课人数 from
Course c left join SC on c.cno=sc.cno
left join student s on s.Sno=SC.Sno
group by c.Cno) as T ON T.Cno=c.Cno
你连关系都没给,怎么查。。。