1、建表
学生表
student
学号,姓名,性别,出生,所在班级
create table student(
sno varchar(20) primary key,
sname varchar(20) not null,
ssex varchar(10) not null,
sbirthday datetime,
sclass varchar(20)
);
教师表
teacher
教师编号,教师名字,教师性别,出生,职称,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)
);
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)
);
2、插入数据
添加学生信息
insert into student value('101','曾华','男','1977-09-01','95033');
insert into student value('102','匡明','男','1975-10-02','95031');
insert into student value('103','王丽','女','1977-01-23','95033');
insert into student value('104','李军','男','1977-02-20','95033');
insert into student value('105','王芳','女','1977-02-10','95031');
insert into student value('106','陆军','男','1977-06-03','95031');
insert into student value('107','李缩','男','1977-02-21','95033');
insert into student value('108','王解','女','1975-02-13','95031');
insert into student value('109','陆稍','男','1977-06-01','95031');
添加教师信息
insert into teacher value('834','李成','男','1958-12-01','副教授','计算机系');
insert into teacher value('856','张旭','男','1968-11-21','讲师','电子工程系');
insert into teacher value('825','王品','女','1972-05-05','助教','计算机系');
insert into teacher value('831','刘冰','女','1977-08-14','助教','电子工程系');
添加课程表
insert into course value('3-245','计算机导论','825');
insert into course value('3-105','操作系统','834');
insert into course value('6-166','数字电路','856');
insert into course value('9-888','高等数学','831');
添加成绩表
insert into score value('103','3-245','86');
insert into score value('105','3-245','75');
insert into score value('109','3-245','68');
insert into score value('103','3-105','92');
insert into score value('105','3-105','88');
insert into score value('109','3-105','76');
insert into score value('101','3-105','91');
insert into score value('102','3-105','78');
insert into score value('103','6-166','85');
insert into score value('105','6-166','79');
insert into score value('109','6-166','81');
3、表数据查看
学生
+-----+--------+------+---------------------+--------+
| sno | sname | ssex | sbirthday | sclass |
+-----+--------+------+---------------------+--------+
| 101 | 曾华 | 男 | 1977-09-01 00:00:00 | 95033 |
| 102 | 匡明 | 男 | 1975-10-02 00:00:00 | 95031 |
| 103 | 王丽 | 女 | 1977-01-23 00:00:00 | 95033 |
| 104 | 李军 | 男 | 1977-02-20 00:00:00 | 95033 |
| 105 | 王芳 | 女 | 1977-02-10 00:00:00 | 95031 |
| 106 | 陆军 | 男 | 1977-06-03 00:00:00 | 95031 |
| 107 | 李缩 | 男 | 1977-02-21 00:00:00 | 95033 |
| 108 | 王解 | 女 | 1975-02-13 00:00:00 | 95031 |
| 109 | 陆稍 | 男 | 1977-06-01 00:00:00 | 95031 |
+-----+--------+------+---------------------+--------+
教师
+-----+--------+------+---------------------+-----------+-----------------+
| tno | tname | tsex | tbirthday | prof | depart |
+-----+--------+------+---------------------+-----------+-----------------+
| 825 | 王品 | 女 | 1972-05-05 00:00:00 | 助教 | 计算机系 |
| 831 | 刘冰 | 女 | 1977-08-14 00:00:00 | 助教 | 电子工程系 |
| 834 | 李成 | 男 | 1958-12-01 00:00:00 | 副教授 | 计算机系 |
| 856 | 张旭 | 男 | 1968-11-21 00:00:00 | 讲师 | 电子工程系 |
+-----+--------+------+---------------------+-----------+-----------------+
课程
+-------+-----------------+-----+
| cno | cname | tno |
+-------+-----------------+-----+
| 3-105 | 操作系统 | 834 |
| 3-245 | 计算机导论 | 825 |
| 6-166 | 数字电路 | 856 |
| 9-888 | 高等数学 | 831 |
+-------+-----------------+-----+
成绩
+-----+-------+--------+
| sno | cno | degree |
+-----+-------+--------+
| 101 | 3-105 | 91 |
| 102 | 3-105 | 78 |
| 103 | 3-105 | 92 |
| 103 | 3-245 | 86 |
| 103 | 6-166 | 85 |
| 105 | 3-105 | 88 |
| 105 | 3-245 | 75 |
| 105 | 6-166 | 79 |
| 109 | 3-105 | 76 |
| 109 | 3-245 | 68 |
| 109 | 6-166 | 81 |
+-----+-------+--------+
4、查询练习
1、查询student表的所有记录
select * from student;
2、查询student表中的所有记录的sname、ssex和sclass列
select sname, ssex, sclass from student;
3、查询教师所有的单位即不重复的depart列
select distinct depart from teacher; //distinct排重
4、查询score表中成绩在60-80之间的所有记录
select * from score where degree between 60 and 80;
select * from score where degree > 60 and degree < 80;
5、查询score表中成绩为85,86或87的记录
select * from score where degree in(85, 86, 87);
6、查询student表中"95031"班，或性别为'女'的同学记录
select * from student where sclass='95031' or ssex='女';
7、以sclass降序查询student表中的所有数据//desc降序 asc升序默认是升序的一般不会写
select * from student order by sclass desc;
8、以cno升序、degree降序查询score表中的所有记录//遇到相同的就降序
select * from score order by cno asc ,degree desc;
9、查询"95031"班级的人数
select count(*) from student where sclass = '95031';
10、查询score表中最高分的学生学号和课程号。(子查询或排序)
select sno, cno from score where degree = (select max(degree) from score);
select sno, cno, degree from score order by degree desc limit 0, 1;
如果按照分数排序，select的时候一定要把degree放进去，0表示从第一行开始数一行，如果是1, 2则表示从第二行开始数两条
11、查询每门课的平均成绩
select * from course;
select avg(degree) from score where cno='3-105';
一门一门查询
下面是写在一句话中
select cno, avg(degree) from score group by cno;
12、查询score表中至少有两名学生选修的并以3开头的课程的平均分数
select cno, avg(degree),count(*) from score group by cno having count(cno)>=2 and cno like '3%';
count(*)表示给出这个group的个数，此题也可以不加
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和degree列
select sno, sname from student;
select sno, cno, degree from score;
需要用第一句话中的sname替换第二行的sno，下面使用多表查寻语句
select sname, cno, degree from student, score where student.sno=score.sno;
15、查寻所有学生的sno, cname和degree
select sno, cname, degree from course, score where course.cno=score.cno;
16、查询所有学生的sname、cname、degree列（来自三张表）
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, course.cno from student, course, score where student.sno=score.sno and course.cno=score.cno;
因为sno有歧义所以要加student.sno，可以用as去改名
17、查询95031班学生每门课的平均分
select cno, avg(degree) from score where sno in (select sno from student where sclass='95031') group by cno;
18、查询选修“3-105”课程的成绩高于109号同学“3-105”成绩的所有同学记录
select * from score where cno='3-105' and degree>(select degree from score where sno='109' and cno='3-105');
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 * from score where degree>(select degree from score where sno='109' and cno='3-105');
20、查询和学号108、101的同学童年出生的所有学生的sno、sname和sbirthday列
select sno,sname,sbirthday from student where year(sbirthday) in (select year(sbirthday) from student where sno in (108,101));
21、查询“张旭”教师任课的学生成绩
select degree from score where cno=(select cno from course where tno=(select tno from teacher where tname='张旭'));
22、查询选修某课程的同学多于5人的教师姓名
select tname from teacher where tno = (select tno from course where cno=(select cno from score group by cno having count(*) > 5));
23、查询95033和95031班全体学生记录
select * from student where sclass in ('95033', '95031');
24、查询85分以上成绩的课程cno
select cno from score where degree>85;
25、查询出“计算机系”教师所有课程的成绩表
select * from score where cno in(select cno from course where tno in (select tno from teacher where depart='计算机系'));
26、查询计算机系和电子工程系不同职称的教师的tname和prof（职称在别的部门没有出现过）
union求并集
select * from teacher where depart='计算机系' and prof not in (select prof from teacher where depart='电子工程系')
union
select * from teacher where depart='电子工程系' and prof not in (select prof from teacher where depart='计算机系');
27、查询选修编号为3-105，且至少高于选修编号为3-245的同学的信息并按照degree降序排列
（至少表示大于其中任意一个，用any）
select * from score where cno = '3-105' and degree > any(select degree from score where cno = '3-245') order by degree desc;
28、查询选修编号为3-105，且成绩高于选修编号为3-245的同学的信息
（且表示大于所有选项，用all）
select * from score where cno = '3-105' and degree > all(select degree from score where cno = '3-245’);
29、查询所有教师和同学的name、sex和birthday(别名as，默认会写第一组的名字所以只要改第一组的名字就ok)
select sname as name, ssex as sex, sbirthday as birthdy from student
union
select tname,tsex,tbirthday from teacher;
30、查询所有女教师和女同学的name、sex和birthday
select sname as name, ssex as sex, sbirthday as birthday from student where ssex = '女'
union
select tname, tsex, tbirthday from teacher where tsex = '女';
31、查询成绩比该课程平均成绩低的同学的成绩表
select cno, avg(degree) from score group by cno;//查询一类课程的平均分
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(任课说明在课程表中有课程)
select tname, depart from teacher where tno in (select tno from course);
33、查询至少有两名男生的班号(加条件分组筛选)
select sclass from student where ssex = '男' group by sclass having count(*)>1;
34、查询student表中不姓王的同学记录
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=当前年份-出生年份
select sname, year(now())-year(sbirthday) from student;
36、查询student表中最大最小sbirthday日期值
select sbirthday from student order by sbirthday;
select max(sbirthday) as '最大',min(sbirthday) as '最小' from student;
37、以班号和年龄从大到小排序查询student表中的全部记录
select * from student order by sclass desc, year(now)-year(sbirthday) desc;
select * from student order by sclass desc, sbirthday;
38、查询男教师及其所教的课程
select cname from course where tno in (select tno from teacher where tsex='男');
39、查询最高分同学的sno、cno和degree列
select * from score where degree = (select max(degree) from score);
40、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');
41、查询和李军同性别并且同班的同学的sname
select sname from student where ssex = (select ssex from student where sname = '李军') and sclass = (select sclass from student where sname = '李军');
42、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 = (select cno from course where cname = '计算机导论');
43、假设使用如下命令建立了一个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(50,59,'E');
查询所有同学的sno、cno和grade列
select sno,cno,grade from score,grade where degree between low and upp;