搞定SQL面试(3)

• 38、查询各个课程及相应的选修人数；

select sc.cid,c.cname,count(distinct sid) as ‘stuCount‘ from sc sc,course c
where sc.cid=c.cid
group by sc.cid,c.cname;

• 39、查询不同课程但成绩相同的学生的学号、课程号、学生成绩；

select distinct sc1.sid,sc1.cid,sc1.score from sc sc1,sc sc2
where sc1.cid!=sc2.cid and sc1.score=sc2.score
order by sc1.score asc;

• 40、查询每门课程成绩最好的前两名；

select sc.cid,c.cname,sc.sid,s.sname,sc.score from student s,sc sc,course c
where s.sid=sc.sid and sc.cid=c.cid and sc.score in
(
    select sc2.score from sc sc2
    where sc2.cid=sc.cid
    order by sc2.score desc limit 2
)
order by sc.cid;

• 41、统计每门课程的学生选修人数（超过10人的课程才统计）。

  要求输出课程号和选修人数，查询结果按人数降序排列，若人数相同，按课程号升序排列

select sc.Cid,COUNT(distinct Sid) as ‘StuCount‘ from SC sc
group by sc.Cid
having COUNT(distinct Sid)>=10
order by StuCount desc,sc.Cid asc

• 42、检索至少选修两门课程的学生学号；

select distinct sc.sid from sc sc
group by sc.sid
having count(sc.cid)>=2;

• 43、查询全部学生都选修的课程的课程号和课程名；

select sc.cid,c.cname from sc sc,course c
where sc.cid=c.cid
group by sc.cid,c.cname
having count(sc.sid)=(select count(distinct s.sid) from student s)

• 44、查询没学过“叶平”老师讲授的任一门课程的学生姓名；

select s.sname from student s where s.sid not in
(
    select sc.sid from sc sc,course c,teacher t
    where sc.cid=c.cid and c.tid=t.tid and t.tname=‘叶平‘
)

• 45、查询两门以上不及格课程的同学的学号及其平均成绩

select sc.sid,avg(ifnull(sc.score,0)) as ‘AvgScore‘ from sc sc
where sc.sid in
(select sc2.sid from sc sc2
where sc2.score<60
group by sc2.sid
having count(sc2.cid)>2
)
group by sc.sid;

• 46、检索“004”课程分数小于60，按分数降序排列的同学学号；（很简单的一题）

select sc.Sid from SC sc
where sc.Cid=‘004‘ and sc.Score<60
order by sc.Score desc

文章转载自 https://www.cnblogs.com/edisonchou/p/3878135.html

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原文地址：https://www.cnblogs.com/linxiaochi/p/9650361.html