mysql查询练习
创建一个数据库
create database sclectTest;
drop database stuTest;
use selecttest;
学生表
Student
学号
姓名
性别
出生年月日
所在班级
create table student(
sno varchar(20) primary key,
sname varchar(20) not null,
ssex varchar(10) not null,
sbirthday datetime,
class varchar(20)
);
教师表
Teacher
教师编号
教师名字
教师性别
出生年月日
所在部门
create table teacher(
tno varchar(20) primary key,
tname varchar(20) not null,
tsex varchar(10) not null,
tbirthday datetime,
prof varchar(20) not null,
depart varchar(20) not null
);
课程表
Course
课程号
课程名称
教师编号.
create table course(
cno varchar(20) primary key,
cname varchar(20) not null,
tno varchar(20) not null,
foreign key(tno) references teacher(tno)
);
use selecttest;
show tables;
成绩表
Score
学号
课程号
成绩
create table score(
sno varchar(20) not null,
cno varchar(20) not null,
degree decimal,
foreign key(sno) references student(sno),
foreign key(cno) references course(cno),
primary key(sno , cno)
);
drop table score;
describe course;
select * from score;
往数据表添加数据
#添加学生数据
insert into student values('101' , '姚云峰' , '男' , '2020-4-1' , '1006');
insert into student values('102' , '党春茹' , '女' , '1999-5-1' , '1006');
insert into student values('103' , '周宇金' , '女' , '2017-8-3' , '1005');
insert into student values('104' , '党浩' , '男' , '2010-5-21' , '1006');
insert into student values('105' , '左岩西' , '男' , '1997-5-5' , '1006');
insert into student values('106' , '二狗' , '女' , '1920-9-8' , '1003');
insert into student values('107' , '张宇豪' , '男' , '1998-8-24' , '1008');
insert into student values('108' , '吴红石' , '男' , '2008-5-30' , '1006');
insert into student values('109' , '耿乐乐' , '女' , '1999-4-1' , '1009');
insert into student values('110' , '王诗越' , '女' , '2020-12-24' , '1007');
insert into student values('111' , '武悦悦' , '男' , '1900-8-1' , '1002');
select * from student;
添加教师表
select * from teacher;
insert into teacher values('001' , '李成' , '男' , '2018-2-2' , '副教授' , '计算机系');
insert into teacher values('002' , '张庆茹' , '女' , '1998-2-2' , '教授' , '信息工程系');
insert into teacher values('003' , '王敏' , '女' , '1963-5-26' , '助教' , '计算机系');
insert into teacher values('004' , '李嘉' , '男' , '1989-2-2' , '教授' , '电子技术系');
添加课程表
insert into course values('3-110' , '计算机导论' , '001');
insert into course values('2-215' , '操作系统原理' , '003');
insert into course values('1-158' , '数据库原理' , '004');
insert into course values('2-113' , '计算机组成原理' , '002');
select * from course;
#添加成绩表
insert into score values('101' , '3-110' , '87');
insert into score values('102' , '2-215' , '75');
insert into score values('103' , '1-158' , '44');
insert into score values('104' , '2-113' , '73');
insert into score values('105' , '3-110' , '86');
insert into score values('106' , '2-113' , '64');
insert into score values('107' , '1-158' , '85');
insert into score values('108' , '3-110' , '78');
insert into score values('109' , '2-215' , '86');
insert into score values('110' , '2-113' , '93');
insert into score values('111' , '1-158' , '74');
insert into score values('111' , '3-110' , '89');
select * from score;
查询联系
1.查询student所有信息
select * from student;
2.查询student表中的所有记录的sname、ssex和class类
select sname , ssex , class from student;
3.查询教师所有单位即不重复的depart列(distinct排除重复)
select depart from teacher;
select distinct depart from teacher;
4.查询score表中成绩在60到80之间的所有记录
方法一：between and
select * from score where degree between 60 and 80;
方法二：运算符比较
select * from score where degree > 60 and degree <80;
5.查询score表中的成绩为85，86，88的记录
表示或的关系
use sclecttest;
select * from score where degree in('86','85','88');
select * from score where degree = 86 or degree = 85;
6.查询student表中95031班或性别为男的同学记录
select * from student where class = '1005' or ssex = '男';
7.以class降序查询student表的所有记录
升序降序如何表达：
asc升序
desc降序
select * from student order by class desc;
不写asc默认也是升序
select * from student order by class;
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班级的学生人数
统计 count
select count(*) from student where class=1005;
select * from student where class=1005;
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);
(1.)找到最高分
select max(degree) from score ;
(2.)找到最高分的sno和cno
select sno , cno from score where degree = (select max(degree) from score) ;
排序的做法：
select sno , cno , degree from score order by degree;
select sno , cno , degree from score order by degree desc;
select sno , cno , degree from score order by degree desc limit 0 , 1;
11.查询每门课的平均成绩
select * from course;
select avg(degree) from score where cno = '1-158';
select avg(degree) from score where cno = '2-113';
select avg(degree) from score where cno = '2-215';
select avg(degree) from score where cno = '3-110';
写在一个sql语句中
select cno , avg(degree) from score group by cno;
select * from score where cno = '1-158';
12.查询score表中的至少有两名学生选修的并以3开头的课程平均分数
select avg(degree) from score group by cno having count(cno)>=2 and cno like '2%';
select cno , avg(degree) , count(cno) from score group by cno having count(cno) >= 2 and cno like '2%';
13.查询分数大于70，小于90的sno列
select sno , degree from score where degree>70 and degree<90;select sno , degree from score where degree between 70 and 90;
14.查询所有学生的sname ， cno ， degree列
查询成绩表
select sno , cno , degree from score;
查询学生表
select sno , sname from student;
`
select sname , cno , degree from student , score where student.sno = score.sno;
15.查询所有学生的sno ， cname ， degree列
select cno , cname from course;
select cno , sno , degree from score;
select sno , cname , degree from course , score where course.cno = score.cno;
16.查询所有学生的sname、cname和degree列
select sname , cname , degree from student , course , score where student.sno = score.sno and course.cno = score.cno;
select sname , cname , degree , student.sno as stu_sno , score.sno , course.cno as cou_cno , course.cno from student , course , score where student.sno = score.sno and course.cno = score.cno;
17.查询1006班学生每门课的平均分
select class from student;
select * from student where class='1006';
select sno from student where class='1006';
select * from score where sno in (select sno from student where class = '1006');
select cno , avg(degree)
from score
where sno in (select sno from student where class = '1006')
group by cno;
18.查询选修3-105课程的成绩高于109号同学 3-105成绩的所有同学
select * from score;
select degree from score where sno = 111 and cno = '3-110';
select * from score where cno = '3-110' and degree<(select degree from score where sno = 111 and cno = '3-110');
19.查询成绩高于学号为109课程号为3-105的成绩的所有记录
select degree from score where cno = '3-110' and sno = 111;
select * from score where degree>(select degree from score where cno='3-110' and sno = 111);
20.查询和学号为108、101的同学童年出生的所有学生的sno ， sname ， sbirthday列
select year(sbirthday) from student where sno = 108 or sno = 101;
select sno , sname , sbirthday from student where year(sbirthday) in (select year(sbirthday) from student where sno = 108 or sno = 101);
21.查询李成教师任课的学生成绩
select tno from teacher where tname = '李成';
select cno from course where tno = (select tno from teacher where tname = '李成');
select degree from score where cno = (select cno from course where tno = (select tno from teacher where tname = '李成'));
22.查询选修某课程的同学人数多余三人的教师姓名
select cno from score group by cno having count(*)>3;
select tno from course where cno = (select cno from score group by cno having count(*)>3) ;
select tname from teacher where tno=(select tno from course where cno = (select cno from score group by cno having count(*)>3) );
- 查询95033班和95031班全体学生的记录
select * from student where class in ('1005' , '1003');
24.查询存在有85分以上成绩的课程cno
select cno , degree from score where degree>85;
25.查询计算机系老师所教课程的成绩表
select * from teacher where depart = '计算机系';
select tno from course;
select cno from course where tno in (select tno from teacher where depart = '计算机系');
select * from score where cno in (select cno from course where tno in (select tno from teacher where depart = '计算机系'));
26.查询计算机系与电子技术系不同职称的教师的tname和prof
–union联合求并集
select * from teacher where depart = '信息工程系' and prof not in (select * from teacher where depart = '电子技术系')
union
select * from teacher where depart = '电子技术系' and prof not in (select *from teacher where depart = '信息工程系');
27.查询选修编号为2-113且成绩至少高于选修编号为3-110的同学的cno , sno , degree , 并按照degree从高到底查询
select * from score where cno = '3-110';
select * from score where cno = '2-113';
select * from score where cno = '2-113' and degree28.查询选修编号为2-113且成绩高于选修编号为3-110的同学的cno , sno , degree
select * from score where cno = '2-113' and degree29.查询所有教师和学生的name，sex ， birthday
select tname as name , tsex as sex , tbirthday as birthday from teacher
union
select sname , ssex , sbirthday from student;
30.查询女教师和女同学的name , sex , birthday
select tname as name , tsex as sex , tbirthday as birthday from teacher where tsex = '女'
union
select sname , ssex , sbirthday from student where ssex = '女';
31.查询成绩比该课程的平均成绩低的同学的成绩表
select cno , avg(degree) from score group by cno;
select * from score ;
select * from score a where degree < (select avg(degree) from score b where a.cno = b.cno);
32.查询所有任课教师的tname和depart
select tname , depart from teacher where tno in (select tno from course);
33.查询至少有两名男生的班级号
select class from student where ssex = '男' group by class having count(*)>1;
34.查询表中不姓王的同学
select * from student where sname not like ('王%');
35.查询student 表中每个学生的姓名和年龄
年龄 = 当前日期-出生年份
查询当前年份
select year(now());
select year(sbirthday) from student;
select sname , year(now()) - year(sbirthday) as age from student;
36.查询student表中的最大和最小值的sbirthday日期值
select sbirthday from student order by sbirthday;
select max(sbirthday) as '最大' , min(sbirthday) '最小' from student;
37.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 ;
38.查询男教师及其所上的课程
select tno from teacher where tsex = '男' ;
select cno from course where tno in (select tno from teacher where tsex = '男');
select cname from course where cno in (select cno from course where tno in (select tno from teacher where tsex = '男'));
39.查询最高分的同学的sno , cno , degree列
select max(degree) from score ;
select sno , cno , degree from score where degree = (select max(degree) from score );
40.查询和姚云峰同性别的所有同学的sname
select ssex from student where sname = '姚云峰';
select sname from student where ssex = (select ssex from student where sname = '姚云峰');
41.查询和姚云峰同性别并且同班的同学的sname
select sname from student
where ssex = (select ssex from student where sname = '姚云峰')
and class = (select class from student where sname = '姚云峰');
42.查询所有选修计算机导论的男同学的成绩表
select * from student;
select sno from student where ssex = '男';
select cno from course where cname = '计算机导论';
select * from score where sno in (select sno from student where ssex = '男') and cno in (select cno from course where cname = '计算机导论');
43.建立grade表
create table grade(
low int(3),
upp int(3),
grade char(1)
);
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');
insert into grade values(0 , 59 , 'E');
select sno , cno , grade from score , grade where degree between low and upp order by grade;