数据库作业

create database 作业
use 作业
--创建学生表
create table Student
(
Sno char(3) primary key  not null,
Sname char(8) not null,
Ssex char(2) not null,
Sbirthday datetime ,
Class char(5)
)

--创建课程表
create table Course
(
Cno char(5) primary key not null,
Cname char(10) not null,
Tno char(3) references Teacher(Tno) not null
)

--创建分数表
create table Score
(
Sno char(3) references Student(Sno) not null,
Cno char(5) references Course(Cno)not null,
Degree decimal(4,1)
)

--创建老师表
create table Teacher
(
Tno char(3) primary key not null,
Tname char(4) not null,
Tsex char(2) not null,
Tbirthday datetime ,
Prof char(6),
Depart varchar(10) not null
)

--给Student插入一系列数据
insert into Student values(108,‘曾华‘,‘男‘,‘1977-09-01‘,95033)
insert into Student values(105,‘匡明‘,‘男‘,‘1975-10-02‘,95031)
insert into Student values(107,‘王丽‘,‘女‘,‘1976-01-23‘,95033)
insert into Student values(101,‘李军‘,‘男‘,‘1976-02-20‘,95033)
insert into Student values(109,‘王芳‘,‘女‘,‘1975-02-10‘,95031)
insert into Student values(103,‘陆君‘,‘男‘,‘1974-06-03‘,95031)
update Student set Sbirthday=‘1977-09-01‘ where Sbirthday=1977-09-01
update Student set Sbirthday=‘1975-10-02‘ where Sbirthday=1975-10-02
update Student set Sbirthday=‘1976-01-23‘ where Sbirthday=1976-01-23
update Student set Sbirthday=‘1976-02-20‘ where Sbirthday=1976-02-20
update Student set Sbirthday=‘1975-02-10‘ where Sbirthday=1975-02-10
update Student set Sbirthday=‘1974-06-03‘ where Sbirthday=1974-06-03
--给Course 插入一系列数据
insert into Course values (‘3-105‘,‘计算机导论‘,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)

--给Score插入一系列数据
insert into Score values(103,‘3-245‘,86)
insert into Score values(105,‘3-245‘,75)
insert into Score values(109,‘3-245‘,68)
insert into Score values(103,‘3-105‘,92)
insert into Score values(105,‘3-105‘,88)
insert into Score values(109,‘3-105‘,76)
insert into Score values(101,‘3-105‘,64)
insert into Score values(107,‘3-105‘,91)
insert into Score values(108,‘3-105‘,78)
insert into Score values(101,‘6-166‘,85)
insert into Score values(107,‘6-166‘,79)
insert into Score values(108,‘6-166‘,81)

--给Teacher 插入一系列数据
insert into Teacher values (804,‘李诚‘,‘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‘,‘电子工程系‘)
update Teacher set Tbirthday =‘1958-12-02‘ where Tbirthday=1958-12-02
update Teacher set Tbirthday =‘1969-03-12‘ where Tbirthday=1969-03-12
update Teacher set Tbirthday =‘1972-05-05‘ where Tbirthday=1972-05-05
update Teacher set Tbirthday =‘1977-08-14‘ where Tbirthday=1977-08-14
select *from Teacher 
select *from Student
select *from Course
select *from Score

--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60到80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85，86或88的记录。
select *from Score where Degree in(85,86,88)
--⑥查询Student表中“95031”班或性别为“女”的同学记录。
select*from Student where Class=95031 or 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“95031”班的学生人数。--聚合函数：针对数据列，计算求和或者计数等一系列算术性操作
select COUNT(*) from Student where Class=95031  --count对计算的结果筛选个数，条数，返回一个数值
--sum(), avg(),max(),min()  括号里面放的是列 ,只有count(*)的括号里面放*
--查一下3-105的最高分  as：起别名
select MAX(degree)as maxfen from Score where Cno=‘3-105‘
--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 )
--排序的方法 select top 1 *from Score order by Degree desc
--11、 查询每门课的平均成绩。 
select AVG(degree) as pingjunfen,cno from Score group by Cno --当分组和聚合结合的时候，先分组，然后对每一组分别进行聚合
--12、查询Score表中至少有5名学生选修的并以3开头的课程的平均分数,并且将成绩这一列排序
select cno,AVG(degree)as degress from Score where Cno like ‘3%‘ group by Cno having COUNT(*)>=5 order by degress
--13、查询分数大于70，小于90的Sno列。
Select Sno from Score where Degree >70 and Degree <90
--14、查询所有学生的Sname、Cno和Degree列。  --表链接
--逗号隔开查两个表，形成笛卡尔积，然后进行where筛选，通过两个表主外键关系筛选
--select sname,cno,degree from Student,Score where student.sno=Score.sno
--正规方法
select sname,Cno,degree from Score  join Student on Score.Sno=Student.Sno
--inner left(把左表全部显示全，右表有关系的显示出来，没关系的显示为空) right 
select Student.Sno,sname,ssex,Student.Class,Score.Sno,Score.Cno,Score.Degree from Student left join Score on Student.Sno=Score.Sno
--15、查询所有学生的Sno、Cname和Degree列。
select score.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 Score join student on Student.Sno=Score.Sno  join Course on Course.Cno=Score.Cno