sql面试题 学生表, 课程表,成绩表,教师表

Student(Sid,Sname,Sage,Ssex) 学生表

Course(Cid,Cname,Tid) 课程表

SC(Sid,Cid,score) 成绩表

Teacher(Tid,Tname) 教师表 

1、查询“001”课程比“002”课程成绩高的所有学生的学号；

   select sid,score from sc where cid='001';

   select sid,socre from sc where cid='002';

   select a.sid from (select sid,score from sc where cid='001') a join (select sid,socre from sc    where cid='002') b on a.sid = b.sid where a.score > b.score;

2  查询平均成绩大于60分的同学的学号和平均成绩；

   select sid,avg(score) from sc group by sid having avg(score)>60;

3  查询所有同学的学号、姓名、选课数、总成绩

   select stu.sid,stu.sname,count(cid),sum(score) from student stu join sc s on stu.sid = s.sid 

4 查询姓“李”的老师的个数；

  select count(tid) from teacher where tname like '李%';

5 查询没学过“叶平”老师课的同学的学号、姓名；

  --叶平老师所带的课程编号

  select cid from course where tid = (select tid from teacher where tname="叶平");

  ---选过叶平老师课程的学生编号(重要)

  select distinct sid from sc where cid in (select cid from course where tid = (select tid from teacher where tname="叶平"));

  ---没有选过叶平老师课程的学生

  select sid,sname from student where sid not in (select distinct sid from sc where cid in (select cid from course where tid = (select tid from teacher where tname="叶平")));

6 查询学过“001”并且也学过编号“002”课程的同学的学号、姓名；

  --学过“001”---

  select sid from sc cid ='001';

  --学过“002”---

  select sid from sc cid ='002';

  --学过'001'同时学过'002'(重要 intersect)---

  select sid,sname from student where sid in ((select sid from sc cid ='001') intersect (select sid from sc cid ='002'));

  --- exists

7 查询学过“叶平”老师所教的所有课的同学的学号、姓名；

  --叶平老师所带的课程编号---------

  select cid from course where tid = (select tid from teacher where tname="叶平");

  --选过叶平老师课程的学生-----(重要)

  select sid,cid from sc where cid in (select cid from course where tid = (select tid from teacher where tname="叶平"));

  --查询学过“叶平”老师所教的所有课的同学的学号----

  select sid from (select count(cid) num from sc where cid in (select cid from course where tid = (select tid from teacher where tname="叶平")) group by sid) where num=(select      count(cid) from course where tid = (select tid from teacher where tname="叶平"))

8 查询所有课程成绩小于60分的同学的学号、姓名；

  -----选出学生的姓名----

  select distinct sid from sc;

  -----选出课程成绩>=60的姓名-----(重要)

  select distinct sid from sc where score>=60;

 -----选出课程成绩<60的姓名

  select distinct sid from sc where sid not in (select distinct sid from sc where score>=60);

9 查询没有学全所有课的同学的学号、姓名；

  -------所有课程数----

  s
4000
elect count(cid) from course;                    ------没有学全所有课--

  select sid,count(cid) from sc group by sid having count(cid)<(select count(cid) from course);

10 查询至少有一门课与学号为“1001”的同学所学相同的同学的学号和姓名；

   ---学号为“1001”的同学所学课程---

   select cid from sc where sid = '1001';

   select distinct sid from sc where cid in (select cid from sc where sid = '1001');

11 删除学习“叶平”老师课的SC表记录；

   delete from sc where cid (select cid from course where tid = (select tid from teacher where tname="叶平"));

12 查询各科成绩最高和最低的分：以如下形式显示：课程ID，最高分，最低分

 

  select cid,max(score),min(score) from sc group by cid