题解 | 查询成绩

select
count(*)
from (
    select
    sum(score) num
    from
    SC
    where sId in (select sId from Student) 
    and cId in (
        select 
        cId 
        from Course 
        where cname in ('语文', '数学', '英语')
    )
    group by sId
) t
where num / 3 > 60