案例-多表查询、子查询实例（有答案）-王明昌博客

如果你对该文章中的内容有疑问/不解,可以点击此处链接提问

要注明问题和此文章链接地址点击此处跳转

1.创建student和score表

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) 
);

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score表。SQL代码如下：

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)
);

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)

);

2.为student表和score表增加记录

向student表插入记录的INSERT语句如下：
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');
#向score表插入记录的INSERT语句如下：
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);

向student表插入记录的INSERT语句如下：

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');

#向score表插入记录的INSERT语句如下：

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);

3.查询student表的所有记录

select * from student;

1 2	select * from student;

4.查询student表的第2条到4条记录

select * from student limit 1,3;

1 2	select * from student limit 1,3;

5.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;

1 2	select id, name, department from student;

6.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';

1 2	select * from student where department = '计算机系' or department = '英语系';

7.从student表中查询年龄18~22岁的学生信息

select * from student where birth between 1995 and 1999;

1 2	select * from student where birth between 1995 and 1999;

8.从student表中查询每个院系有多少人

select count(*) as num ,department from student GROUP BY department;

1 2	select count(*) as num ,department from student GROUP BY department;

9.从score表中查询每个科目的最高分

select max(grade),c_name  from score GROUP BY c_name;

1 2	select max(grade),c_name from score GROUP BY c_name;

10.查询李四的考试科目（c_name）和考试成绩（grade）

SELECT  sc.c_name , sc.grade, st.name
FROM student as st , score as sc
where st.id = sc.stu_id and st.name = '李四';

SELECT sc.c_name , sc.grade, st.name