关于MySQL的基本查询(多表查询等)

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)

);

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)

);

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);

3.查询student表的所有记录

select * from student;

4.查询student表的第2条到4条记录

select * from student where id between 902 and 904;

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

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 '中文系');

7.从student表中查询年龄18~22岁的学生信息

select * from student where YEAR(NOW())-birth>=18 and YEAR(NOW())-birth<=22;

8.从student表中查询每个院系有多少人

SELECT COUNT(*) "人数",department "专业" from student GROUP BY (department);

9.从score表中查询每个科目的最高分

SELECT c_name "专业" , max(grade) 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 c_name "专业" , grade from score where stu_id=(select id from student where name='李四');

11.用连接的方式查询所有学生的信息和考试信息

select * from student INNER JOIN score ON student.id=score.stu_id;

12.计算每个学生的总成绩

select stu_id "学号",SUM(grade) from score GROUP BY (stu_id);

13.计算每个考试科目的平均成绩

select c_name "专业",AVG(grade) from score GROUP BY (c_name);

14.查询计算机成绩低于95的学生信息

 select * from student where id=any(select stu_id from score where grade<=95 and c_name='计算机');

15.查询同时参加计算机和英语考试的学生的信息

select student.* from student,score as s1,score as s2 where student.id=s1.stu_id AND s1.c_name='英语' AND student.id=s2.stu_id AND s2.c_name='计算机';

16.将计算机考试成绩按从高到低进行排序

 select * from score where c_name='计算机' ORDER BY (grade) DESC;

17.从student表和score表中查询出学生的学号，然后合并查询结果

select * from student,score where student.id=score.stu_id;

18.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 name '姓名',department '院系',c_name '考试科目',grade '成绩' from score,student where student.id=score.stu_id AND (name LIKE '王%' OR name LIKE '张%');

19.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 name '姓名',department '院系',c_name '考试科目',grade '成绩' from score,student where student.id=score.stu_id AND (address LIKE '湖南省%');