MySQL经典案例50题

数据准备

建表、插入数据

-- 学生表
CREATE TABLE Student(
s_id VARCHAR(20),
s_name VARCHAR(20) NOT NULL DEFAULT'',
s_birth VARCHAR(20) NOT NULL DEFAULT'',
s_sex VARCHAR(10) NOT NULL DEFAULT'',
PRIMARY KEY(s_id)
);
-- 课程表
CREATE TABLE Course(
c_id VARCHAR(20),
c_name VARCHAR(20) NOT NULL DEFAULT'',
t_id VARCHAR (20) NOT NULL,
PRIMARY KEY(c_id)
);
-- 教师表
CREATE TABLE Teacher(
t_id VARCHAR(20),
t_name VARCHAR(20) NOT NULL DEFAULT'',
PRIMARY key(t_id)
);
-- 成绩表
CREATE TABLE Score(
s_id VARCHAR(20),
c_id VARCHAR(20),
s_score INT(3),
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');
-- 插入课程表测试数据
insert into Course values('01' , '语文' , '02'); 
insert into Course values('02' , '数学' , '01'); 
insert into Course values('03' , '英语' , '03');
-- 插入教师表测试数据
insert into Teacher values('01' , '张三'); 
insert into Teacher values('02' , '李四'); 
insert into Teacher values('03' , '王五');
-- 插入成绩表测试数据
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' , '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);

题目

– 1

、查询"01"课程比"02"课程成绩高的学生的信息及课程分数

SELECT
stu.*,sco.s_score
FROM student stu
LEFT JOIN score sco ON stu.s_id=sco.s_id
WHERE stu.s_id IN(
SELECT
stu.s_id
FROM score sco1
WHERE sco1.c_id='01'
AND sco1.s_score > (
SELECT
sco2.s_score
FROM score sco2
WHERE sco1.s_id=sco2.s_id
AND sco2.c_id='02'
)
);

– 2

、查询"01"课程比"02"课程成绩低的学生的信息及课程分数

SELECT
stu.*,sco.s_score
FROM student stu
LEFT JOIN score sco on stu.s_id=sco.s_id
WHERE stu.s_id in(
SELECT
sco1.s_id
FROM score sco1
where sco1.c_id='01'
AND sco1.s_score <(
SELECT
sco2.s_score
FROM score sco2
where sco2.c_id='02'
AND sco1.s_id=sco2.s_id
)
);

– 3

、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

SELECT
stu.s_id,stu.s_name,avg(sco.s_score) AS '平均成绩'
FROM student stu LEFT JOIN score sco ON stu.s_id=sco.s_id
GROUP BY stu.s_id
HAVING avg(sco.s_score)>=60;

– 4

、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
stu.s_id,stu.s_name,avg(sco.s_score) AS '平均成绩'
FROM student stu LEFT JOIN score sco ON stu.s_id=sco.s_id
GROUP BY stu.s_id
HAVING avg(sco.s_score)<60
or avg(sco.s_score) is null;

– 5

、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
stu.s_id,
stu.s_name,
count(sco.c_id) AS '选课总数',
sum(sco.s_score) as '总成绩'
from student stu 
LEFT JOIN score sco ON stu.s_id=sco.s_id
GROUP BY stu.s_id;

– 6

、查询"李"姓老师的数量

SELECT COUNT(*) FROM teacher t WHERE t.t_name LIKE '李%';

– 7

、查询学过"张三"老师授课的同学的信息

SELECT
stu.*
FROM student stu 
LEFT JOIN score sco on stu.s_id=sco.s_id
LEFT JOIN course cou ON sco.c_id=cou.c_id
LEFT JOIN teacher tea ON cou.t_id=tea.t_id
where tea.t_name='张三';

– 8

、查询没学过"张三"老师授课的同学的信息

SELECT stu.* FROM student stu WHERE stu.s_id IN(
SELECT te.t_id FROM teacher te
left JOIN course co ON co.t_id = te.t_id
left JOIN score so ON co.c_id=so.c_id
LEFT JOIN student st ON st.s_id = so.s_id
WHERE te.t_name <> '张三' );

– 9

、查询学过编号为"01"并且也学过编号为"02"的课程的同学的信息

SELECT
stu.*
FROM score sco 
LEFT JOIN student stu ON stu.s_id=sco.s_id
WHERE sco.c_id='01'
AND sco.s_id =(
SELECT
sco1.s_id
from score sco1 
WHERE sco1.c_id='02'
and sco.s_id=sco1.s_id)

10

、查询学过编号为"01"但是没有学过编号为"02"的课程的同学的信息

SELECT
stu.*
FROM score sco 
LEFT JOIN student stu ON stu.s_id=sco.s_id
WHERE sco.c_id='01'
AND stu.s_id NOT IN(
SELECT
sco1.s_id
FROM score sco1
WHERE sco1.c_id='02'
AND stu.s_id=sco1.s_id)

11

、查询没有学全所有课程的同学的信息

SELECT
stu.*
FROM student stu 
LEFT JOIN score sco ON sco.s_id=stu.s_id
where stu.s_id NOT IN(
SELECT
sco1.s_id
FROM score sco1
WHERE sco1.c_id='01'OR sco1.c_id='02' OR sco1.c_id='03'
AND sco1.s_id=sco.s_id)

12

、查询至少有一门课与学号为"01"的同学所学相同的同学的信息

SELECT
stu.*
FROM student stu 
LEFT JOIN score sco ON sco.s_id=stu.s_id
WHERE sco.c_id IN (
SELECT 
sco1.c_id
FROM score sco1 
WHERE sco.s_id='01')
GROUP BY stu.s_id

13

、查询和"01"号的同学学习的课程完全相同的其他同学的信息

SELECT 
stu.*
FROM student stu
WHERE stu.s_id IN(
SELECT
sco.s_id
FROM score sco 
WHERE sco.c_id IN(
SELECT
sco1.c_id
FROM score sco1
WHERE sco1.s_id='01')
GROUP BY sco.s_id
HAVING COUNT(*)=(
SELECT
COUNT(*)
FROM score sco2
WHERE sco2.s_id='01')
AND SUM(sco.c_id)=(
SELECT
SUM(sco3.c_id)
FROM score sco3
WHERE sco3.s_id='01'))

14

、查询没学过"张三"老师讲授的任一门课程的学生姓名

SELECT * FROM student WHERE s_id NOT IN(
SELECT st.s_id FROM student st
LEFT JOIN score sc ON st.s_id=sc.s_id
LEFT JOIN course co ON sc.c_id= co.c_id
LEFT JOIN teacher te ON co.t_id = te.t_id
WHERE t_name = '张三');

15

、查询两门及其以上不及格课程的同学的学号，姓名及其平均成绩

SELECT
stu.s_id,stu.s_name,avg(sco.s_score)
FROM student stu
LEFT JOIN score sco ON stu.s_id=sco.s_id
WHERE sco.s_id IN(
SELECT 
sco1.s_id
FROM score sco1 WHERE sco1.s_score < 60 
GROUP BY sco1.s_id
HAVING COUNT(sco1.s_id>=2))
GROUP BY stu.s_id

16

、检索"01"课程分数小于60，按分数降序排列的学生信息

SELECT
stu.*
FROM student stu 
LEFT JOIN score sco ON sco.s_id=stu.s_id
WHERE sco.c_id='01'
AND sco.s_score<60
ORDER BY sco.s_score DESC

17

、按平均成绩从高到低显示所有学生的所有课程的成绩以及平均成绩

SELECT
stu.*,
avg(sco.s_score) AS '平均成绩',
(SELECT s_score from score WHERE c_id='01' AND s_id=stu.s_id) as '数学成绩',
(SELECT s_score from score WHERE c_id='02' AND s_id=stu.s_id) as '语文成绩',
(SELECT s_score from score WHERE c_id='03' AND s_id=stu.s_id) as '英语成绩'
FROM student stu
LEFT JOIN score sco on sco.s_id=stu.s_id
GROUP BY sco.s_id
ORDER BY avg(sco.s_score) DESC

18

.查询各科成绩最高分、最低分和平均分：以如下形式显示：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
cou.c_id,cou.c_name,
(SELECT s_score FROM score WHERE c_id=cou.c_id ORDER BY s_score DESC LIMIT 1)AS '最高分',
(SELECT s_score FROM score WHERE c_id=cou.c_id ORDER BY s_score LIMIT 1)AS '最低分',
((SELECT COUNT(*) FROM score WHERE c_id=cou.c_id AND s_score>= 60)/(SELECT COUNT(*) FROM score WHERE c_id=cou.c_id))AS'及格率',
((SELECT COUNT(*) FROM score WHERE c_id=cou.c_id AND s_score >=70 AND s_score<80)/(SELECT COUNT(*)FROM score WHERE c_id=cou.c_id))AS '中等率',
((SELECT COUNT(*) FROM score WHERE c_id=cou.c_id AND s_score >=80 AND s_score<90)/(SELECT COUNT(*)FROM score WHERE c_id=cou.c_id))AS '优良率',
((SELECT COUNT(*) FROM score WHERE c_id=cou.c_id AND s_score >=90)/(SELECT COUNT(*) FROM score WHERE c_id=cou.c_id))AS '优秀率'
FROM course cou LEFT JOIN score sco ON cou.c_id=sco.c_id
GROUP BY cou.c_id

19

、按各科成绩进行排序，并显示排名(实现不完全)

SELECT
c_id,s_id,s_score,IF(@prec=c_id,@rank:=@rank+1,@rank:=1)AS '名次',@prec:=c_id
FROM score,(SELECT @rank:=0)r,(SELECT @prec:=-1)p
ORDER BY c_id,s_score DESC

20

、查询学生的总成绩并进行排名

SELECT s_id , SUM(s_score) sum1 FROM score GROUP BY s_id ORDER BY sum1 DESC

21

、查询不同老师所教不同课程平均分从高到低显示

SELECT
cou.c_name,avg(sco.s_score)
FROM course cou 
LEFT JOIN score sco ON cou.c_id=sco.c_id
GROUP BY cou.c_id
ORDER BY avg(sco.s_score) DESC

22

、查询所有课程的成绩第2名到第3名的学生信息及该课程成绩

SELECT
*
FROM(
SELECT 
c_id,
s_id,
s_score,
IF(@prec=c_id,@rank:=@rank+1,@rank:=1)AS 名次,
@prec:=c_id
FROM score
ORDER BY c_id,s_score DESC)t WHERE 名次=2 OR 名次=3;

23

、统计各科成绩各分数段人数：课程编号,课程名称,[100-85],[85-70],[70-60],[0-60]及所占百分比

SELECT
cou.c_id AS '课程编号',cou.c_name AS '课程名称',
((SELECT COUNT(*) FROM score WHERE c_id = cou.c_id AND (s_score>85 AND s_score<=100))/(SELECT COUNT(*) FROM score WHERE c_id=cou.c_id)) AS '[100-85]',
((SELECT COUNT(*) FROM score WHERE c_id = cou.c_id AND (s_score>70 AND s_score<=85))/(SELECT COUNT(*) FROM score WHERE c_id=cou.c_id)) AS '[85-70]',
((SELECT COUNT(*) FROM score WHERE c_id = cou.c_id AND (s_score>60 AND s_score<=70))/(SELECT COUNT(*) FROM score WHERE c_id=cou.c_id)) AS '[70-60]',
((SELECT COUNT(*) FROM score WHERE c_id = cou.c_id AND (s_score>=0 AND s_score<=60))/(SELECT COUNT(*) FROM score WHERE c_id=cou.c_id)) AS '[60-0]'
FROM course cou LEFT JOIN score sco ON cou.c_id = sco.c_id
GROUP BY cou.c_id;

24

、查询学生平均成绩及其名次

SELECT
s_name,avg_score,@num:=@num+1 '名次' 
FROM
(SELECT
stu.*,
avg(s_score) avg_score,
(SELECT @num:=0) '名次'
FROM score sco 
LEFT JOIN student stu ON sco.s_id=stu.s_id
GROUP BY stu.s_id
ORDER BY avg(sco.s_score) DESC)t

25

、查询各科成绩前 三名的记录

SELECT
*
FROM(
SELECT
c_id,
s_id,
s_score,
IF(@prec=c_id,@rank:=@rank+1,@rank:=1)AS 名次,
@prec:=c_id
FROM score,
(SELECT @rank:=0)r,
(SELECT @prec:=-1)p
ORDER BY c_id,s_score DESC)t 
WHERE 名次 = 1 OR 名次 = 2 OR 名次 = 3;

26

、查询每门课程被选修的学生数

SELECT
c_name,
COUNT(s_id)AS '学生数'
FROM score sc LEFT JOIN course co ON co.c_id=sc.c_id
GROUP BY sc.c_id

27

、查询出只有两门课程的全部学生的学号和姓名

SELECT 
s_sex,
COUNT(*) 
FROM student
GROUP BY s_sex

28

、查询男生、女生人数

SELECT 
s_sex,
COUNT(*) 
FROM student
GROUP BY s_sex

29

、查询名字中含有"风"字的学生信息

SELECT * FROM student WHERE s_name LIKE '%风%'

30

、查询同名同性学生名单，并统计同名人数

SELECT
*,
COUNT(stu.s_name)AS '同名人数'
FROM student stu
WHERE stu.s_name IN(
SELECT 
stu1.s_name
FROM student stu1
WHERE stu.s_id != stu1.s_id) 
GROUP BY stu.s_name

31

、查询1990年出生的学生名单

SELECT
c_id,
avg(s_score)
FROM score
GROUP BY c_id
ORDER BY avg(s_score) DESC,c_id

32

、查询每门课程的平均成绩，结果按平均成绩降序排列，平均成绩相同时，按课程编号升序排列

SELECT
c_id,
avg(s_score)
FROM score
GROUP BY c_id
ORDER BY avg(s_score) DESC,c_id

33

、查询平均成绩大于等于85的所有学生的学号、姓名和平均成绩

SELECT
sc.s_id,
st.s_name,
avg(s_score)AS '平均成绩'
FROM score sc LEFT JOIN student st ON st.s_id=sc.s_id
GROUP BY sc.s_id 
HAVING avg(s_score) >= 85

34

、查询课程名称为"数学"，且分数低于60的学生姓名和分数

SELECT
co.c_name,
st.s_name,
sc.s_score
FROM score sc 
LEFT JOIN course co ON sc.c_id=co.c_id
LEFT JOIN student st ON sc.s_id=st.s_id
WHERE co.c_name='数学' AND sc.s_score<60
-- 嵌套查询
SELECT
st.s_name,
t.s_score
FROM student st INNER JOIN
(SELECT
*
FROM score WHERE c_id IN(
SELECT c_id 
FROM course 
WHERE c_name = '数学' )
AND s_score<60) t ON t.s_id=st.s_id

35

、查询所有学生的课程及分数情况；

SELECT
st.s_name,
co.c_name,
sc.s_score
FROM score sc 
LEFT JOIN course co ON sc.c_id=co.c_id
LEFT JOIN student st ON sc.s_id=st.s_id

36

、查询任何一门课程成绩在70分以上的姓名、课程名称和分数；

SELECT
stu.s_name,
co.c_name,
sc.s_score
FROM score sc 
LEFT JOIN student stu ON stu.s_id=sc.s_id
LEFT JOIN course co ON co.c_id=sc.c_id
WHERE sc.s_score > 70

37

、查询不及格的课程

SELECT
co.c_name,
stu.s_name,
sc.s_score
FROM score sc 
LEFT JOIN student stu ON stu.s_id=sc.s_id
LEFT JOIN course co ON co.c_id=sc.c_id
WHERE sc.s_score < 60

38

、查询课程编号为01且课程成绩在80分以上的学生的学号和姓名；

SELECT
s_id,
s_name
FROM student
WHERE s_id IN
(SELECT
s_id
FROM score
WHERE c_id = '01' AND s_score > 80)

39

、求每门课程的学生人数

SELECT
co.c_name,
sc.c_id,
COUNT(sc.s_id)AS '学生人数'
FROM score sc 
LEFT JOIN course co ON co.c_id=sc.c_id
GROUP BY sc.c_id

40

、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
st.*,
co.c_name,
sc.s_score
FROM score sc 
LEFT JOIN student st ON st.s_id=sc.s_id
LEFT JOIN course co ON sc.c_id=co.c_id
LEFT JOIN teacher te ON te.t_id=co.t_id
WHERE te.t_name='张三'
ORDER BY sc.s_score DESC
LIMIT 1

41

、查询不同课程成绩相同的学生的学生编号、课程编号、学生成绩

SELECT
stu.s_id,
sc.c_id,
sc.s_score
FROM student stu
LEFT JOIN score sc ON stu.s_id=sc.s_id
WHERE sc.s_id IN(
SELECT
sc1.s_id
FROM score sc1
LEFT JOIN score sc2 ON sc1.s_id=sc2.s_id AND sc1.c_id!=sc2.c_id
WHERE sc2.s_score=sc1.s_score 
GROUP BY sc1.s_id
)
GROUP BY stu.s_id

42

、查询每门功成绩最好的前两名

SELECT
sc.*
FROM score sc 
WHERE (
SELECT COUNT(*) FROM score sc1
WHERE sc.c_id=sc1.c_id AND sc.s_score<=sc1.s_score
)<=2
ORDER BY sc.c_id,sc.s_score DESC

43

、统计每门课程的学生选修人数（超过5人的课程才统计）。要求输出课程号和选修人数，查询结果按人数降序排列，若人数相同，按课程号升序排列

with t AS(
SELECT
sc.c_id,
COUNT(sc.s_id)AS '选修人数'
FROM score sc 
LEFT JOIN course co ON co.c_id=sc.c_id
GROUP BY sc.c_id
ORDER BY COUNT(sc.s_id) DESC,sc.c_id )
SELECT t.c_id,t.`选修人数` FROM t WHERE t.`选修人数` > 5

44

、检索至少选修两门课程的学生学号

SELECT
sc.s_id,
COUNT(sc.c_id)
FROM score sc 
GROUP BY sc.s_id
HAVING COUNT(sc.c_id)>=2

45

、查询选修了全部课程的学生信息

SELECT
*
FROM student stu
WHERE stu.s_id IN( 
SELECT
sc.s_id
FROM score sc 
GROUP BY sc.s_id
HAVING COUNT(sc.c_id)=3)

46

、查询各学生的年龄

SELECT
s_name,
s_birth,
(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))
FROM student

47

、查询本周过生日的学生

SELECT * FROM student WHERE WEEK(DATE_FORMAT(NOW(),'%Y%m%d'))=WEEK(s_birth)

48

、查询下周过生日的学生

SELECT * FROM student WHERE WEEK(DATE_FORMAT(NOW(),'%Y%m%d'))+1=WEEK(s_birth)

49

、查询本月过生日的学生

SELECT * FROM student WHERE MONTH(DATE_FORMAT(NOW(),'%Y%m%d'))=MONTH(s_birth)

50

、查询下月过生日的学生

SELECT * FROM student WHERE MONTH(DATE_FORMAT(NOW(),'%Y%m%d'))+1=MONTH(s_birth)

SELECT
*
FROM student stu
WHERE stu.s_id IN( 
SELECT
sc.s_id
FROM score sc 
GROUP BY sc.s_id
HAVING COUNT(sc.c_id)=3)

46

、查询各学生的年龄

SELECT
s_name,
s_birth,
(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))
FROM student

47

、查询本周过生日的学生

SELECT * FROM student WHERE WEEK(DATE_FORMAT(NOW(),'%Y%m%d'))=WEEK(s_birth)

48

、查询下周过生日的学生

SELECT * FROM student WHERE WEEK(DATE_FORMAT(NOW(),'%Y%m%d'))+1=WEEK(s_birth)

49

、查询本月过生日的学生

SELECT * FROM student WHERE MONTH(DATE_FORMAT(NOW(),'%Y%m%d'))=MONTH(s_birth)

50

、查询下月过生日的学生

SELECT * FROM student WHERE MONTH(DATE_FORMAT(NOW(),'%Y%m%d'))+1=MONTH(s_birth)