数据分析---mysql查询练习

相关精彩专题链接：数据成就更好的你

一、数据源

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

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');

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

insert into Course values('01' , '语文' , '02');

insert into Course values('02' , '数学' , '01');

insert into Course values('03' , '英语' , '03');

3.教师表 Teacher(t_id,t_name) –教师编号,教师姓名

insert into Teacher values('01' , '张三');

insert into Teacher values('02' , '李四');

insert into Teacher values('03' , '王五');

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

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);

二、查询练习

1.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

或者

select c.s_id,s_name,s_sex, s_birth,a.score01,b.score02 from Student c

join (select s_id,s_score score01 from Score where c_id="01")a on c.s_id=a.s_id

left join (select s_id,s_score score02 from Score where c_id="02")b on c.s_id=b.s_id

where a.score01>b.score02;

2.查询平均成绩大于等于60分的同学的学生编号和学生姓名和平均成绩，平均成绩降序

select student.s_id, student.s_name,temp.avgscore from student

left join (select score.s_id,round(avg(s_score),2) avgscore from score group by s_id)temp

on student.s_id=temp.s_id

where temp.avgscore>=60

Order by temp.avgscore desc

3.查询平均成绩小于60分的同学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 student.s_id, student.s_name,temp.avgscore from student

left join (select score.s_id,round(avg(s_score),2) avgscore from score group by s_id)temp

on student.s_id=temp.s_id

where (temp.avgscore<=60) or (temp.avgscore is null);

4.查询所有同学的学生编号、学生姓名、选课总数、所有课程的总成绩

select a.s_id,a.s_name,count(b.c_id) as course_num,sum(b.s_score) as all_score from

student a

left join score b on a.s_id=b.s_id

GROUP BY a.s_id,a.s_name;

5.询课程ID，课程name，最高分，最低分，平均分，及格率，中等率，优良率，优秀率

--及格为>=60，中等为：70-80，优良为：80-90，优秀为：>=90

select a.c_id,b.c_name,MAX(s_score) as 最高分,MIN(s_score) as 最低分,ROUND(AVG(s_score),2) as 平均分,

ROUND(100*(SUM(case when a.s_score>=60 then 1 else 0 end)/count(*)),2) as 及格率,

ROUND(100*(SUM(case when a.s_score>=70 and a.s_score<=80 then 1 else 0 end)/count(*)),2) as 中等率,

ROUND(100*(SUM(case when a.s_score>=80 and a.s_score<=90 then 1 else 0 end)/count(*)),2) as 优良率,

ROUND(100*(SUM(case when a.s_score>=90 then 1 else 0 end)/count(*)),2) as 优秀率

from score a left join course b on a.c_id = b.c_id GROUP BY a.c_id,b.c_name

6.查询学生的总成绩并进行排名

select c.*,row_number() over(order by c.allscore desc) as "排名" from

(select a.s_id,a.s_name,sum(b.s_score) allscore from student a

left join score b on a.s_id=b.s_id

group by a.s_id,a.s_name)c;

7.查询各科成绩的前三名

select c.c_name,b.s_name,a.s_score,a.rank1 from

(select score.*,row_number() over(partition by c_id order by s_score desc) as rank1 from score)a

left join student b on a.s_id=b.s_id

left join course c on a.c_id=c.c_id

where a.rank1<4

8.查询学生报课程，课程数量，每个学生所报的课程显示在同一行

select

a.s_id,a.s_name,

group_concat(c.c_name) as "所报课程",

count(distinct(c.c_name)) as "课程数量" from Student a

left join Score b on a.s_id=b.s_id

left join Course c on b.c_id=c.c_id

group by a.s_id,a.s_name;

9.查询各学生的年龄

select s_id,s_name,s_birth,s_sex,

(DATE_FORMAT(NOW(),'%Y')-DATE_FORMAT(s_birth,'%Y') -

(case when DATE_FORMAT(NOW(),'%m%d')>DATE_FORMAT(s_birth,'%m%d') then 0 else 1 end)) as age

from student;

10.查询学过"张三"老师授课的同学的信息

select a.* from student a

left join score b on a.s_id=b.s_id

left join course c on b.c_id=c.c_id

left join teacher d on c.t_id=d.t_id

where d.t_name="张三"

11.查询没学过"张三"老师讲授的任一门课程的学生姓名

select m.* from student m left join

(select c.s_id from teacher a

join course b on a.t_id=b.t_id and a.t_name="张三"

join score c on b.c_id=c.c_id)n

on m.s_id=n.s_id

where n.s_id is null；

13.查询选修"张三"老师所授课程的学生中，成绩最高的学生信息及其成绩

select c.* from

(

select a.s_id,a.s_name,c.c_name,b.s_score,d.t_name,rank() over(order by b.s_score desc) rf

from student a

left join score b on a.s_id=b.s_id

left join course c on b.c_id=c.c_id

left join teacher d on c.t_id=d.t_id

where d.t_name="张三"

)c where c.rf=1;

14查询1990年出生的学生名单

select s_name ,s_birth from student where s_birth like '1990%';

数据分析---mysql查询练习

推荐阅读更多精彩内容