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%');
