创建一个student表格：
create table student(
id int(10) not null unique primary key,
name varchar(20) not null,
sex varchar(4),
birth year,
department varchar(20),
address varchar(50)
);
创建一个score表格
create table score(
id int(10) not null unique primary key auto_increment,
stu_id int(10) not null,
c_name varchar(20),
grade int(10)
);
在student表中插入数据
INSERT INTO student VALUES( 901,'张老大', '男',1985,'计算机系', '北京市海淀区');
INSERT INTO student VALUES( 902,'张老二', '男',1986,'中文系', '北京市昌平区');
INSERT INTO student VALUES( 903,'张三', '女',1990,'中文系', '湖南省永州市');
INSERT INTO student VALUES( 904,'李四', '男',1990,'英语系', '辽宁省阜新市');
INSERT INTO student VALUES( 905,'王五', '女',1991,'英语系', '福建省厦门市');
INSERT INTO student VALUES( 906,'王六', '男',1988,'计算机系', '湖南省衡阳市');
查看student表
在score表中插入数据
INSERT INTO score VALUES(NULL,901, '计算机',98);
INSERT INTO score VALUES(NULL,901, '英语', 80);
INSERT INTO score VALUES(NULL,902, '计算机',65);
INSERT INTO score VALUES(NULL,902, '中文',88);
INSERT INTO score VALUES(NULL,903, '中文',95);
INSERT INTO score VALUES(NULL,904, '计算机',70);
INSERT INTO score VALUES(NULL,904, '英语',92);
INSERT INTO score VALUES(NULL,905, '英语',94);
INSERT INTO score VALUES(NULL,906, '计算机',90);
INSERT INTO score VALUES(NULL,906, '英语',85);
1.查询student表中所有记录
select * from student;
2.查询student表的第2条到4条记录
select * from student limit 1,2;
3.从student表查询所有学生的学号(id)、姓名(name) 和院系(department)的信息
select id,name,department from student;
4.从student表中查询计算机系和英语系的学生的信息
select * from student where department='计算机系' or department='英语系';
5.从student表中查询年龄33~37岁的学生信息（1990）
select *from student where birth >1984 and birth <1990;
6.从student表中查询每个院系有多少人
select department ,count(*) as zong
from student
group by department;
7.从score表中查询每个科目的最高分
select c_name,max(grade) as zuigao from score group by c_name;
8.查询李四的考试科曰(c name) 和考试成绩(grade)
select student.name,score.grade,score.c_name
from student
join score on student.id=score.stu_id
where name='李四';
9.用连接的方式查询所有学生的信息和考试信息
select stu.id,stu.name,stu.sex,stu.birth,stu.department,stu.address,sc.c_name,sc.grade
from student as stu join score as sc on stu.id=sc.stu_id;
10.计算每个学生的总成绩
select stu.name,sum(grade)as zong
from student as stu join score as sc on stu.id=sc.stu_id group by stu.name;
11.计算每个考试科目的半均成绩
select stu.name,avg(grade)as zong
from student as stu join score as sc
on stu.id=sc.stu_id group by stu.name;
12.查询计算机成绩低于95的学生信息
select stu.id,stu.name,stu.sex,stu.birth,stu.department,stu.address,sc.c_name,sc.grade
from student as stu
join score as sc on stu.id=sc.stu_id
where sc.grade < 95 and sc.c_name='计算机';
13.查询同时参加计算机和英语考试的学生的信息
select stu.id, stu.name, stu.sex, stu.birth, stu.department, stu.address
from student AS stu
join score AS sc1 ON stu.id = sc1.stu_id
join score AS sc2 ON stu.id = sc2.stu_id
where sc1.c_name = '计算机' AND sc2.c_name = '英语';
14.将计算机考试成绩按从高到低进行排
select *from student as stu
join score as sc
on stu.id=sc.stu_id where sc.c_name='计算机' order by sc.grade desc;
15.从student表和score表中查询出学生的学号，然后合并查询结果
select stu.id,stu.name from student as stu
join score as sc
on stu.id=sc.stu_id;
16.查询姓张或者姓王的同学的姓名、院系和考试科目及成绩
select stu.name,stu.department,sc.c_name,sc.grade from student as stu
join score as sc
on stu.id=sc.stu_id
where stu.name like'张%' or stu.name like'王%';
17.查询都是湖南的学生的姓名、年龄、院系和考试科目及成绩
select stu.name,stu.department,sc.c_name,sc.grade,stu.address from student as stu
join score as sc
on stu.id=sc.stu_id
where stu.address like '湖南%'；
