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  • 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','','1977-09-01',95033)
    insert into Student values(105,'匡明','','1975-10-02',95031)
    insert into Student values(107,'王丽','','1976-01-23',95033)
    insert into Student values(101,'李军','','1976-02-20',95033)
    insert into Student values(109,'王芳','','1975-02-10',95031)
    insert into Student values(103,'陆君','','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','',1958-12-02,'副教授','计算机系')
    insert into Teacher values (856,'张旭','',1969-03-12,'讲师','电子工程系')
    insert into Teacher values (825,'王萍','',1972-05-05,'助教','计算机系')
    insert into Teacher values (831,'刘冰','',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=''
    --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
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  • 原文地址:https://www.cnblogs.com/lk-kk/p/4446891.html
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