面試題一SQL語句

面試題一SQL語句

學生表：

Student(sid,sname,sage,ssex) --學生編號，學生姓名，出生日期，學生性別

課程表：

Course(cid,cname,tid) --課程編號，課程名稱，教師編號

教師表

Teacher(tid,tname) --教師編號，教師姓名

成績表

Sc(sid,cid,score) --學生編號，課程編號，分數

SQL語句：

1. 查詢“01”課程比“02”課程成績高的學生的信息及課程分數

   select a.*,b.score,c.score
   from student a
   left join sc b on a.sid=b.sid and b.cid='01'
   left join sc c on a.sid=c.sid and c.cid='02'
   where b.score>c.score
   

2. 查詢平均成績大於等於60分的同學的學生編號，學生姓名和平均成績

   select a.sid，a.sname，avg(sc.score) avg_score
   from student a,sc
   where a.sid = sc.sid
   group by a.sid,a.sname
   having avg_score>=60
   order by a.sid;
   

3. 查詢所有學生的學生編號，學生姓名，選課總數，所有課程訂單總成績

   select a.sid,a.sname,count(b.cid),sum(b.score)
   from student a
   left join sc b
   on a.sid=b.sid
   group by a.sid,a.sname
   order by a.sid
   

4. 統計課程分01最高的前三名學生信息

   select a.sname,sc.score,sc.cid
   from student a
   join sc 
   on a.sid=sc.sid
   where sc.cid='01'
   order by sc.score desc limit 3;
   

5. 統計每個學生的選課總數

   select a.sid,a.sname,count(b.cid)
   from student a
   left join sc b
   on a.sid=b.sid
   group by a.sid,a.sname
   

6. 查詢沒學過“張三”老師授課的學生信息

   select a.*
   from student a
   left join sc b
   where not exists(
       select *
       from course c
       inner join teacher d
       on c.tid=d.tid
       inner join sc e
       on c.cid=e.cid
       where d.tname='張三'
       and e.sid = a.sid
   )
   group by 1,2,3,4;
   

7. 查詢學過編號“01”並且也學過編號“02”的課程的學生信息

   select a.*
   from student a
   inner join sc b
   on a.sid = b.sid and b.cid ='01'
   inner join sc c
   on a.sid = c.sid on c.cid='02';