题解 | 查询成绩

select count(*)

from(
    select s.sid,sum(SC.score) as sum_SC
    from Student s
    join SC
    on s.sid = SC.sid
    join Course c
    on SC.cid = c.cid

    where  c.cid in ('1','2','3')
    group by s.sid
    having sum_SC>180
) as avg_sc

写爽了，一个是关于是不是要子查询的判断

另一个是差点忽略了还要是语数英的课程