例题：学习数据库查询。学生信息表的创建，主外键关系，以及45道题的查询实例。主要知识点在讲页45页，和讲页65页

create database shujuku

use shujuku

use cangku

go

--注意事项：外键对本关系不一定是键

--2：创建外键时，链接表的主关键字已经确立

--3：当创建外部键后，外部键的取值必须来源于主键值

--4：要想删除主键表时，必须先删除外键表信息

 

 

create table student--学生表

(

sno varchar(50) not null primary key ,--学生主键

sname varchar(50)not null,

ssex varchar(50)not null,

sbirthdy date ,

class varchar(50)

)

select *from student

insert into student values('1','曾华','男','1987-09-01','95033')

insert into student values('2','李明','男','1985-10-01','95031')

insert into student values('3','王丽','女','1986-02-20','95033')

insert into student values('4','李军','男','1986-01-23','95033')

insert into student values('5','王芳','女','1985-02-10','95031')

insert into student values('6','肖君','男','1991-06-03','95031')

drop table student

go

create table course--课程表

cno varchar(50)not null primary key,

cname varchar(50)not null,

tno varchar(50) references teacher(tno)not null, --教师外键

)

insert into course values('3-105','计算机','825')

insert into course values('3-245','操作系统','804')

insert into course values('6-166','数字电路','856')

insert into course values('9-888','高等数学','831')

select *from course

drop table course

go                              --cno课程编号  --sno学生编号--tno教师编号

create table score--成绩表

(

sno varchar(50) references student(sno)not null, --学生外键

cno varchar(50) references course(cno)not null,    --课程外键

degree decimal(4,1)

)

select *from score

insert into score values('1','3-245',86)

insert into score values('1','3-245',75)

insert into score values('2','3-245',68)

insert into score values('2','3-105',56)

insert into score values('3','3-105',76)

insert into score values('3','3-105',84)

insert into score values('4','3-105',85)

insert into score values('4','3-105',86)

insert into score values('5','3-105',87)

insert into score values('5','6-166',88)

insert into score values('6','6-166',89)

insert into score values('6','6-166',80)

drop table score

go

create table teacher--教师表

(

tno varchar(50) primary key not null,  --教师主键

tname varchar(50) not null,

tsex varchar(50)not null,

tbirthday date ,

prof varchar(50),

depart varchar(50)not null

)

insert into teacher values('804','李斌','男','1958-12-02','副教授','计算机系')

insert into teacher values('856','张旭','男','1969-03-12','讲师','电子工程系')

insert into teacher values('825','王萍','女','1972-05-05','助教','计算机系')

insert into teacher values('831','刘冰','女','1977-08-14','助教','电子工程')

select *from teacher

drop table teacher

go

1、查询Student表中的所有记录的Sname、Ssex和Class列。

select sname,ssex,class from student

2、查询教师所有的单位即不重复的Depart列。

select distinct depart from teacher

3、查询Student表的所有记录。

select*from student

4、查询Score表中成绩在到之间的所有记录。

select*from score where DEGREE between 60 and 80

5、查询Score表中成绩为，或的记录。

select*from  score where DEGREE in (85,86,88)

6、查询Student表中“”班或性别为“女”的同学记录。

select*from student where class='95031' and ssex='女'

7、以Class降序查询Student表的所有记录。

select*from student order by class desc

8、以Cno升序、Degree降序查询Score表的所有记录。

select*from score order by cno asc ,DEGREE desc

9、查询“”班的学生人数。

select COUNT(*) from student where class='95031'

10、查询Score表中的最高分的学生学号和课程号。（子查询或者排序）

select sno,cno from score where degree=(select MAX(degree) from score)

select top 1* sno,cno from score order by degree desc                  --为什么这样做不行      

11、查询每门课的平均成绩。

select avg(degree) from score where cno='3-245'

12、查询Score表中至少有名学生选修的并以开头的课程的平均分数。      --重点题目

select cno,AVG(degree) degrees from score where cno like '3%' group by cno having COUNT(cno)>

13、查询分数大于，小于的Sno列。

select sno from  score where DEGREE between 70 and 90

14、查询所有学生的Sname、Cno和Degree列。

select sname ,cno,degree from student join score on student.sno=score.sno

15、查询所有学生的Sno、Cname和Degree列。                --重点题目

select sno,cname,DEGREE from score join course on score.cno=course.cno

16、查询所有学生的Sname、Cname和Degree列。

select sname,cname,DEGREE from student join score on student.sno=score.sno

join course on course.cno=score.cno

17、查询“”班学生的平均分。

select avg(degree) from score where sno in (select sno from student where class='95033')

18、假设使用如下命令建立了一个grade表：    --重点题目

create table grade

(

low  int not null,

upp  int not null,

[rank]  varchar (50)

)

insert into grade values(90,100,'A')

insert into grade values(80,89,'B')

insert into grade values(70,79,'C')

insert into grade values(60,69,'D')

select  sno,cno,rank from score join grade on degree between low and upp order by rank  desc --表连接方法

select sno,cno,(select RANK from grade where score.degree between low and upp ) 级别 from score--子查询

现查询所有同学的Sno、Cno和rank列。

19、 查询选修“-105”课程的成绩高于“”号同学成绩的所有同学的记录。   --重点题目

select * from score where cno='3-105' and DEGREE>(select degree from score where sno='2'and cno='3-105')

20、查询score中选学多门课程的同学中分数为非最高分成绩的记录。--重点题目，看不懂

--select x.* from score x where degree<(select max(y.degree) from score y where  y.sno=x.sno)

select *from score where sno in (select sno from score group by sno

having COUNT (*)>1)

and degree not in (select MAX(degree)from score where sno in(select sno from  score group by sno having COUNT(sno)>1))

--查询每门课最高分学生之外的其他学生分数信息

 select*from score a where DEGREE not in(select MAX(degree) from score b cno having a.cno=b.cno)

 select*from score a where DEGREE not in (select MAX(degree)from score b where a.cno=b.cno )

 --剔除选多门课的每门课最高分

 select*from score a where DEGREE not in (select MAX(degree)from score b where a.cno=b.cno ) and sno in

 (select cno from score group by cno having COUNT(*) >1)

21、查询成绩高于学号为“”、课程号为“-105”的成绩的所有记录。

select *from score where DEGREE>(select DEGREE from score where sno='2' and cno='3-105')

22、查询和学号为的同学同年出生的所有学生的Sno、Sname和Sbirthday列。--重点题目

select sno,sname,sbirthdy from student where YEAR(sbirthdy)=(select YEAR(sbirthdy)from student where sno='3')

23、查询“张旭“教师任课的学生成绩。

select degree from score where cno in(select cno from course where tno=(select tno from  teacher where tname='张旭'))

24、查询选修某课程的同学人数多于人的教师姓名。

select tname from teacher where tno in(select tno from course where cno =

(select cno from score group by cno having COUNT(cno)>5))

25、查询班和班全体学生的记录。 --重点题目

select *from student join score on student.sno=score.sno where class in('95033','95031')

26、 查询存在有分以上成绩的课程Cno.

select cno from score where DEGREE>85

27、查询出“计算机系“教师所教课程的成绩表。

select *from score where cno in(select cno from course where tno in(select tno from teacher where depart='计算机系'))

28、查询“计算机系”与“电子工程系“不同职称的教师的Tname和Prof

 select tname ,prof from teacher where prof not in( select prof from teacher group by prof having COUNT(prof)>1)

)

29、查询选修编号为“-105“课程且成绩至少高于选修编号为“-245”的同学的Cno、Sno和Degree,并按Degree从高到低次序排序。

select*from score where cno='3-105'  and degree>(select MAX(degree) from score where cno='3-245') order by DEGREE asc

30、查询选修编号为“-105”且成绩高于选修编号为“-245”课程的同学的Cno、Sno和Degree.

select*from score where cno='3-105'and DEGREE>(select MAX(degree)from score where cno='3-245')

31、查询所有教师和同学的name、sex和birthday.

select sname ,ssex,sbirthdy from student

union

select tname,tsex,tbirthday from teacher

32、查询所有“女”教师和“女”同学的name、sex和birthday.

select sname,ssex,sbirthdy from student where ssex='女'

union

select tname,tsex,tbirthday from teacher where tsex='女'

33、查询成绩比该课程平均成绩低的同学的成绩表。

select *from score where degree <(select AVG(degree)from score )

34、查询所有任课教师的Tname和Depart.

select tname from teacher where tno in (select tno from course where cno  in (select cno from score))                                  

35 、查询所有未讲课的教师的Tname和Depart.

select tname from teacher where tno not in(select tno from course where cno in (select cno from score ))

36、查询至少有名男生的班号。

select class from student group by class having COUNT(class)>=2

37、查询Student表中不姓“王”的同学记录。

select*from student where sname not like '王%'

38、查询Student表中每个学生的姓名和年龄。

select sname,DATEDIFF(YEAR,sbirthdy,getdate()) age from student

39、查询Student表中最大和最小的Sbirthday日期值。

select MAX(sbirthdy),MIN(sbirthdy)from student

40、以班号和年龄从大到小的顺序查询Student表中的全部记录。

select*from student order by class desc,sbirthdy asc

41、查询“男”教师及其所上的课程。

select tname ,cname from teacher join course on teacher.tno=course.tno  where tsex='男'

42、查询最高分同学的Sno、Cno和Degree列。

select*from score where DEGREE in(select MAX(degree)from score)

43、查询和“李军”同性别的所有同学的Sname.

select sname from student where ssex in  (select ssex from student where sname='李军')

44、查询和“李军”同性别并同班的同学Sname.

select sname from student where ssex in (select ssex from student where sname='李军')and

 class in(select class from student where sname='李军')

45、查询所有选修“计算机导论”课程的“男”同学的成绩表。

select *from score where sno in(select sno from student where ssex='男')

 and cno in (select cno from course where cname='计算机')