mysql一些代码和例题

Q1：Mysql数据库的一些简单实例

create database if not exists StudentsDB default charset utf8;
use StudentsDB;
#Student(学生表)
create table Student
(
    Sno char(3) not null primary key comment '学号',
    Sname char(8) not null comment '学生姓名',
    Ssex char(2) not null comment '学生性别',
    Sbirthday datetime comment '学生出生年月',
    Class char(5) comment '学生所在班级'
);
#给学生表插入数据
insert into Student values
('108','曾华','男','1977-09-01','95033'),
('105','匡明','男','1975-10-02','95031'),
('107','王丽','女','1976-01-23','95033'),
('101','李军','男','1976-02-20','95033'),
('109','王芳','女','1975-02-10','95031'),
('103','陆军','男','1974-06-03','95031');
insert into Student values('111','老张','男','1974-06-03','95031');
insert into Student values('111','老罗','男','1974-06-03','95031');
select *from student;
#教工表
create table Teacher
(
    Tno char(3) not null primary key comment '教工编号',
    Tname char(4) not null comment '教工姓名',
    Tsex char(2) not null comment '教工性别',
    Tbirthday datetime comment '教工出生年月',
    Prof char(6) comment '职称',
    Depart varchar(10) not null comment '教工所在部门'
);
#老师表数据
insert into Teacher values
('804','李诚','男','1958-12-02','副教授','计算机系'),
('856','张旭','男','1969-03-12','讲师','电子工程系'),
('825','王萍','女','1972-05-05','助教','计算机系'),
('831','刘冰','女','1977-08-14','助教','电子工程系');
insert into Teacher values('832','老张','男','1977-08-14','助教','电子工程系');
select *from teacher;
#课程表
create table Course
(
    Cno char(5) not null primary key comment '课程号',
    Cname varchar(10) not null comment '课程名称',
    Tno char(3) comment '教工编号',
    foreign key(Tno) references Teacher(Tno)
);
#课程表数据
insert into Course values
('3-105','计算机导论','825'),
('3-245','操作系统','804'),
('6-166','数字电路','856'),
('9-888','高等数学','831');
#课程表数据
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');
select *from Course;
#成绩表
create table Score
(
    Sno char(3) comment '学号',
    foreign key(Sno) references Student(Sno),
    Cno char(5) comment '课程号',
    foreign key(Cno) references Course(Cno),
    Degree Decimal(4,1) comment '成绩'
);
#分数表
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('103','3-245','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');
insert into Score values('111','6-166','81');
select *from Score;
#查询Student表中的所有记录的Sname、Ssex和Class列。
select Sname '姓名',Ssex '性别',Class '班级' from Student;
#查询教师所有的单位即不重复的Depart列。
select distinct Depart from Teacher;
#查询Student表的所有记录
select *from Student;
#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;
#查询Score表中成绩为85，86或88的记录。
select *from Score where Degree in(85,86,88);
#查询Student表中“95031”班或性别为“女”的同学记录。
select *from Student where Class='95031' and Ssex='女';
#以Class降序查询Student表的所有记录。
select *from Student order by Class desc;
#以Cno升序、Degree降序查询Score表的所有记录。
select *from Score order by Cno,Degree desc;
#查询“95031”班的学生人数。
select count(*) from Student where Class='95031';
#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）
#查询语句查询出一个或者一列结果，可以作为其他查询语句的参数来使用，就是子查询，就是查询的嵌套。
select Degree from Score limit 0,2;
select *from Score limit 0,2;
#select Sno,Cno from Score where Degree in(select Degree from Score order by Degree desc limit 0,1); 
select Sno,Cno from Score where Degree=(select max(Degree) from Score);
select Sno,Cno from Score where Degree in(select Degree from Score); 
select Sno,Cno from Score where Degree in(select Degree d from
(select Degree from Score order by Degree desc limit 0,3)as d); 
#查询每门课的平均成绩，要按照课程分组group by，然后求没门课平均avg
select *from Course;
select *from Score;
select Cname '课程名称',avg(Degree) '成绩' from Score s inner join Course c on s.Cno=c.Cno group by c.Cno;
#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。
#Like模糊查询 3%以3开头 having只能跟在group by 后面
select Cno '课程编号',avg(Degree) '平均分数' from Score where Cno like '3%' group by Cno having count(Sno)>5;
#查询分数大于70，小于90的Sno列。
Select *from Student;
Select *from Score;
select *from Score where Degree>70 and Degree<90;
#查询所有学生的Sname、Cno和Degree列。
select *from Student;
Select *from Score;
Select *from Course;
select Sname,Cno,Degree from Score sc inner join Student s on sc.Sno=s.Sno;
#查询所有学生的Sno、Cname和Degree列。
select s.Sno,c.Cname,sc.Degree from Score sc inner join Student s on sc.Sno=s.Sno 
inner join Course c on sc.Cno=c.Cno;
#查询所有学生的Sname、Cname和Degree列。
select s.sName,c.Cname,sc.Degree from Score sc inner join Course c on sc.Cno=c.Cno 
inner join Student s  on sc.Sno=s.Sno;
#查询“95033”班学生的平均分。
select *from Student;
select avg(sc.Degree) from Score sc inner join Student s on sc.Sno=s.Sno where S.Class='95033'; 
#查询选修“3-105”课程的成绩高于“109”号同学成绩的所有同学的记录。
#select *from Score sc inner join Course c on sc.Cno=c.Cno where c.Cno='3-105' where sc.Degree ;
select *from Score sc inner join Course c on sc.Cno=c.Cno inner join Student s on sc.Sno=s.Sno
where c.Cno='3-105' and sc.Degree>(select max(Degree) from Score where Sno='109');
#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。
#注意有having时再加where要放于后面
select *from score group by Sno having count(Cno)>1 and Degree<>max(Degree);
select *from score;
#查询成绩高于学号为“109”、课程号为“3-105”的成m绩的所有记录。
select *from score where Sno='109' and Cno='3-105';
#查询和学号为108的同学同年出生的所有学生的Sno、Sname和Sbirthday列。
select Sno,Sname,Sbirthday from Student;
#查询“张旭“教师任的学生成绩。
select *from Teacher;
select Degree from Score sc inner join Course c on sc.Cno=c.Cno 
inner join Teacher t on c.Tno=t.Tno where Tname='王萍';
#查询选修某课程的同学人数多于5人的教师姓名
select Tname from Score sc inner join Course c on sc.Cno=c.Cno inner join Teacher t on c.Tno=t.Tno 
group by Tname having count(Sno)>5;
#查询95033班和95031班全体学生的记录。
select *from Student where Class='95033' or Class='95031';
#查询存在有85分以上成绩的课程Cno.
select *from Score group by Cno having Degree>85;
#查询出“计算机系“教师所教课程的成绩表。
select Depart '计算机系',Cname '课程',Degree '成绩' from Score sc inner join Course c on sc.Cno=c.Cno 
inner join Teacher t on c.Tno=t.Tno where Depart='计算机系';
#从一个表复制数据到另一个表中
insert into Teacher(Tno,Tname,Tsex,Tbirthday,Prof)
select Sno,Sname,Ssex,Sbirthday,Class from Student;
select *from Teacher;
#查询“计算机系”与“电子工程系“不同职称的教师的Tname和Prof。
select *from Teacher;
select *from Course;
select Tname,Prof from Teacher where Depart='计算机系' or Depart='电子工程系';
#查询选修编号为“3-105“课程且成绩至少高于选修编号为“3-245”的同
select *from Score sc inner join Course c on sc.Cno=c.Cno inner join Student s on sc.Sno=s.Sno
where sc.Degree >(select Degree from Score where Cno='3-245')and c.Cno='3-105';
select *from Score sc inner join Course c on sc.Cno=c.Cno inner join Student s on sc.Sno=s.Sno
where sc.Degree >(select min(Degree) from Score where Cno='3-245') and c.Cno='3-105';
#查询选修编号为“3-105”且成绩高于选修编号为“3-245”课程的同学的Cno、Sno和Degree. ?
select c.Cno,S.Sno,sc.Degree from Score sc inner join Course c on sc.Cno=c.Cno inner join Student s on sc.Sno=s.Sno
where sc.Degree >=(select max(Degree) from Score where Cno='3-245') and c.Cno='3-105';
#查询所有教师和同学的name、sex和birthday.
select Sname,Ssex,Sbirthday from Student union Select Tname,Tsex,Tbirthday from Teacher;
#查询所有“女”教师和“女”同学的name、sex和birthday.
select Sname,Ssex,Sbirthday from Student where Ssex='女' union Select Tname,Tsex,Tbirthday from Teacher where Tsex='女';
# 查询成绩比该课程平均成绩低的同学的成绩表。
select avg(sc.Degree) from Score sc inner join Course c on sc.Cno=c.Cno 
inner join Student s on sc.Sno=s.Sno group by c.Cno;
#select *from Score sc inner join Student s on sc.Sno=s.Sno 
#inner join Course c on sc.Cno=c.Cno where sc.Degree<();
select *from Score s1 where s1.Degree<(
    select avg(s2.Degree) from Score s2 where s1.Cno=s2.Cno
);
#查询所有任课教师的Tname和Depart.
select Tname,Depart from Teacher;
#查询所有未讲课的教师的Tname和Depart.
select *from Teacher where Tno not in(select Tno from Course);
#查询至少有2名男生的班号。
select Class from Student group by Class having count(Class)>=2 and count(Ssex)>=4;
#查询不姓王的同学信息
select *from Student where Sname not like '王%';
#查询Student表中每个学生的姓名和年龄。
select Sname,Ssex from Student;
#查询Student表中最大和最小的Sbirthday日期值。
select max(Sbirthday),min(Sbirthday) from Student;
#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,Sbirthday desc;
#查询“男”教师及其所上的课程。
select distinct Cname,Tname from Score sc inner join course c on sc.Cno=c.Cno 
inner join Teacher t on c.Tno=t.Tno where Tsex='男'; 
#查询最高分同学的Sno,Cno和Degree列。
select max(Degree) from Score;
select Sno,Cno,Degree from Score where Degree=(select max(Degree) from Score);
#查询所有选修“计算机导论”课程的“男”同学的成绩表。
select Cname,Ssex,Sname,Degree from Score sc inner join Course c on sc.Cno=c.Cno inner join Student s on sc.Sno=s.Sno
where Cname='计算机导论' and Ssex='男';
#查询和“李军”同性别的所有同学的Sname.
select Sname from Student where Ssex=(select Ssex from Student where Sname='李军');

大家可以把数据库建好以后，测试一下