MySQL经典练手面试题

建立数据库

表和字段

1.学生表 
Student(s_id,s_name,s_birth,s_sex) –学生编号,学生姓名, 出生年月,学生性别 

2.课程表 
Course(c_id,c_name,t_id) – –课程编号, 课程名称, 教师编号

3.教师表
Teacher(t_id,t_name) –教师编号,教师姓名

4.成绩表 
Score(s_id,c_id,s_score) –学生编号,课程编号,分数

测试数据

--学生表
DROP TABLE IF EXISTS `student`;
CREATE TABLE `student`(
    `s_id` VARCHAR(20),
    `s_name` VARCHAR(20) NOT NULL comment '姓名',
    `s_birth` VARCHAR(20) NOT NULL comment '生日',
    `s_sex` VARCHAR(10) NOT NULL comment '性别',
    PRIMARY KEY(`s_id`)
);
--课程表
DROP TABLE IF EXISTS `course`;
CREATE TABLE `course`(
    `c_id`  VARCHAR(20),
    `c_name` VARCHAR(20) NOT NULL comment '课程名',
    `t_id` VARCHAR(20) NOT NULL comment '学生id',
    PRIMARY KEY(`c_id`)
);
--教师表
DROP TABLE IF EXISTS `teacher`;
CREATE TABLE `teacher`(
    `t_id` VARCHAR(20),
    `t_name` VARCHAR(20) NOT NULL comment '教师名称',
    PRIMARY KEY(`t_id`)
);
--成绩表
DROP TABLE IF EXISTS `score`;
CREATE TABLE `score`(
    `s_id` VARCHAR(20),
    `c_id`  VARCHAR(20) NOT NULL comment '课程名',
    `s_score` INT(3) NOT NULL comment '成绩',
    PRIMARY KEY(`s_id`,`c_id`)
);
--插入学生表测试数据
insert into student values('01' , '赵雷' , '1990-01-01' , '男');
insert into student values('02' , '钱电' , '1990-12-21' , '男');
insert into student values('03' , '孙风' , '1990-05-20' , '男');
insert into student values('04' , '李云' , '1990-08-06' , '男');
insert into student values('05' , '周梅' , '1991-12-01' , '女');
insert into student values('06' , '吴兰' , '1992-03-01' , '女');
insert into student values('07' , '郑竹' , '1989-07-01' , '女');
insert into student values('08' , '王菊' , '1990-01-20' , '女');
--课程表测试数据
insert into course values('01' , '语文' , '02');
insert into course values('02' , '数学' , '01');
insert into course values('03' , '英语' , '03');
 
--教师表测试数据
insert into teacher values('01' , '张三');
insert into teacher values('02' , '李四');
insert into teacher values('03' , '王五');
 
--成绩表测试数据
insert into score values('01' , '01' , 80);
insert into score values('01' , '02' , 90);
insert into score values('01' , '03' , 99);
insert into score values('02' , '01' , 70);
insert into score values('02' , '02' , 60);
insert into score values('02' , '03' , 80);
insert into score values('03' , '01' , 80);
insert into score values('03' , '02' , 80);
insert into score values('03' , '03' , 80);
insert into score values('04' , '01' , 50);
insert into score values('04' , '02' , 30);
insert into score values('04' , '03' , 20);
insert into score values('05' , '01' , 76);
insert into score values('05' , '02' , 87);
insert into score values('06' , '01' , 31);
insert into score values('06' , '03' , 34);
insert into score values('07' , '02' , 89);
insert into score values('07' , '03' , 98);

练习题和sql实现语句

一、查询"01"课程比"02"课程成绩高的学生的信息及课程分数

select a.* ,b.s_score as 01_score,c.s_score as 02_score 
from student a join score b 
on a.s_id=b.s_id and b.c_id='01' left join score c 
on a.s_id=c.s_id and c.c_id='02' 
where b.s_score>c.s_score 

查询结果：

二、查询"01"课程比"02"课程成绩低的学生的信息及课程分数

select a.* ,b.s_score as 01_score,c.s_score as 02_score 
from student a join score b 
on a.s_id=b.s_id and b.c_id='01' left join score c 
on a.s_id=c.s_id and c.c_id='02' 
where b.s_score<c.s_score 

查询结果：

三、查询平均成绩大于等于60分的同窗的学生编号和学生姓名和平均成绩

select a.s_id,a.s_name,round(avg(b.s_score),2) as avg_score 
from student a join score b on a.s_id=b.s_id
group by a.s_id,a.s_name having round(avg(b.s_score),2)>=60;

查询结果：

四、查询平均成绩小于60分的同窗的学生编号和学生姓名和平均成绩-- (包括有成绩的和无成绩的)

select a.s_id,a.s_name,round(avg(b.s_score),2) as avg_score 
from student a join score b on a.s_id=b.s_id
group by a.s_id,a.s_name having round(avg(b.s_score),2)<60;

查询结果：

五、查询全部同窗的学生编号、学生姓名、选课总数、全部课程的总成绩

select a.s_id as '学生编号',a.s_name as '学生姓名',
sum(b.c_id) as '选课总数',
sum(b.s_score) as '课程总成绩'
from student a join score b on a.s_id=b.s_id
GROUP BY a.s_id,a.s_name

查询结果：

六、查询"李"姓老师的数量

select count(t_id) as '老师数量'
from teacher 
where t_name LIKE '李%';

查询结果：

七、查询学过"张三"老师授课的同窗的信息

select a.* from 
    student a join score s on a.s_id = s.s_id 
    where s.c_id in(
        select c_id from course where t_id = (
            select t_id from teacher where t_name='张三'));

查询结果：没有符合结果

八、查询没学过"张三"老师授课的同窗的信息

select * from 
    student c 
    where c.s_id not in(
        select a.s_id from student a join score b on a.s_id=b.s_id where b.c_id in(
            select c_id from course where t_id =(
                select t_id from teacher where t_name = '张三')));

查询结果：

九、查询学过编号为"01"而且也学过编号为"02"的课程的同窗的信息

十、查询学过编号为"01"可是没有学过编号为"02"的课程的同窗的信息