连接查询

 1 create table score
 2 (    code int primary key identity(1001,1),
 3     yu decimal(18,2),
 4     shu decimal(18,2),
 5     ying decimal(18,2),
 6 )
 7 create table stu
 8 (    scode int primary key identity(1001,1),
 9     sname varchar(18),
10     banji varchar(18),
11     yujiao int,
12     shujiao int,
13     yingjiao int,
14 )
15 create table tch
16 (    tcode int primary key identity(1,1),
17     tname varchar(18),
18     kemu varchar(18),
19 )
20 insert into score values(99,88,77)
21 insert into score values(88,77,66)
22 insert into score values(77,66,55)
23 insert into score values(66,55,44)
24 insert into score values(55,44,33)
25 insert into score values(89,79,69)
26 insert into score values(79,69,59)
27 insert into score values(59,49,39)
28 insert into tch values(‘玲玲‘,‘语文‘)
29 insert into tch values(‘凌凌‘,‘语文‘)
30 insert into tch values(‘灵灵‘,‘语文‘)
31 insert into tch values(‘铃铃‘,‘数学‘)
32 insert into tch values(‘媛媛‘,‘数学‘)
33 insert into tch values(‘元元‘,‘数学‘)
34 insert into tch values(‘圆圆‘,‘英语‘)
35 insert into tch values(‘方方‘,‘英语‘)
36 insert into tch values(‘芳芳‘,‘英语‘)
37 insert into stu values(‘A‘,‘一班‘,2,4,8)
38 insert into stu values(‘B‘,‘一班‘,1,5,7)
39 insert into stu values(‘C‘,‘二班‘,3,6,9)
40 insert into stu values(‘D‘,‘二班‘,2,4,8)
41 insert into stu values(‘E‘,‘三班‘,1,5,7)
42 insert into stu values(‘F‘,‘三班‘,3,6,9)
43 insert into stu values(‘G‘,‘四班‘,2,4,7)
44 insert into stu values(‘H‘,‘四班‘,1,5,9)
45 select *from score
46 select *from stu
47 select *from tch
48 
49 select *from stu where  yingjiao=(select  tcode from tch where tname=‘圆圆‘)
50 select stu.banji, score.shu from stu,score  where score.code=stu.scode
51 --查询此次考试语文最高分的学生信息
52 select*from stu where scode=(select code from score where yu=(select MAX(yu) from score))
53 --查询此次考试数学最低分的老师信息
54  select * from tch where tcode in (
55  (select yujiao from stu where scode=(select code from score where shu=(select MIN(shu)from score))),
56  (select shujiao from stu where scode=(select code from score where shu=(select MIN(shu)from score))),
57  (select yingjiao from stu where scode=(select code from score where shu=(select MIN(shu)from score)))
58  )
59  --查询汇总成一个表：各门课分数，学生姓名，班级，任课老师的姓名
60  select stu.sname,banji,score.yu,shu,ying,
61  (select tname from tch where tcode=yujiao) as 语文,
62   (select tname from tch where tcode=shujiao) as 数学,
63    (select tname from tch where tcode=yingjiao) as 英语
64   from stu join  score on stu.scode=score.code
65 --查询每个班数学最高分
66 select banji,MAX(shu) from stu join score on stu.scode=score.code group by banji
67 --查询语文平均分最高的班级的老师信息
68 select * from tch where tcode=
69 (    select top 1 yujiao from stu where banji=
70 (    select top 1 banji from stu join score 
71     on stu.scode=score.code 
72     group by banji order by AVG(yu) desc
73 )
74 )