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

SELECTstu.*,sco.s_scoreFROM student stuLEFT JOIN score sco ON stu.s_id=sco.s_idWHERE stu.s_id IN(SELECTstu.s_idFROM score sco1WHERE sco1.c_id='01'AND sco1.s_score > (SELECTsco2.s_scoreFROM score sco2WHERE sco1.s_id=sco2.s_idAND 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

SELECTstu.*,sco.s_scoreFROM student stuLEFT JOIN score sco on stu.s_id=sco.s_idWHERE stu.s_id in(SELECTsco1.s_idFROM score sco1where sco1.c_id='01'AND sco1.s_score <(SELECTsco2.s_scoreFROM score sco2where 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

SELECTstu.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_idGROUP BY stu.s_idHAVING 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)

SELECTstu.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_idGROUP BY stu.s_idHAVING avg(sco.s_score)<60or 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

SELECTstu.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_idGROUP 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

SELECTstu.*FROM student stu LEFT JOIN score sco on stu.s_id=sco.s_idLEFT JOIN course cou ON sco.c_id=cou.c_idLEFT JOIN teacher tea ON cou.t_id=tea.t_idwhere 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 teleft JOIN course co ON co.t_id = te.t_idleft JOIN score so ON co.c_id=so.c_idLEFT JOIN student st ON st.s_id = so.s_idWHERE 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

SELECTstu.*FROM score sco LEFT JOIN student stu ON stu.s_id=sco.s_idWHERE sco.c_id='01'AND sco.s_id =(SELECTsco1.s_idfrom 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

SELECTstu.*FROM score sco LEFT JOIN student stu ON stu.s_id=sco.s_idWHERE sco.c_id='01'AND stu.s_id NOT IN(SELECTsco1.s_idFROM score sco1WHERE 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

SELECTstu.*FROM student stu LEFT JOIN score sco ON sco.s_id=stu.s_idwhere stu.s_id NOT IN(SELECTsco1.s_idFROM score sco1WHERE 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

SELECTstu.*FROM student stu LEFT JOIN score sco ON sco.s_id=stu.s_idWHERE sco.c_id IN (SELECT sco1.c_idFROM 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 stuWHERE stu.s_id IN(SELECTsco.s_idFROM score sco WHERE sco.c_id IN(SELECTsco1.c_idFROM score sco1WHERE sco1.s_id='01')GROUP BY sco.s_idHAVING COUNT(*)=(SELECTCOUNT(*)FROM score sco2WHERE sco2.s_id='01')AND SUM(sco.c_id)=(SELECTSUM(sco3.c_id)FROM score sco3WHERE 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 stLEFT JOIN score sc ON st.s_id=sc.s_idLEFT JOIN course co ON sc.c_id= co.c_idLEFT JOIN teacher te ON co.t_id = te.t_idWHERE 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

SELECTstu.s_id,stu.s_name,avg(sco.s_score)FROM student stuLEFT JOIN score sco ON stu.s_id=sco.s_idWHERE sco.s_id IN(SELECT sco1.s_idFROM score sco1 WHERE sco1.s_score < 60 GROUP BY sco1.s_idHAVING 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

SELECTstu.*FROM student stu LEFT JOIN score sco ON sco.s_id=stu.s_idWHERE sco.c_id='01'AND sco.s_score<60ORDER 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

SELECTstu.*,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 stuLEFT JOIN score sco on sco.s_id=stu.s_idGROUP BY sco.s_idORDER 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

SELECTcou.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_idGROUP BY cou.c_id

19

、按各科成绩进行排序，并显示排名(实现不完全)

SELECTc_id,s_id,s_score,IF(@prec=c_id,@rank:=@rank+1,@rank:=1)AS '名次',@prec:=c_idFROM score,(SELECT @rank:=0)r,(SELECT @prec:=-1)pORDER 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

SELECTcou.c_name,avg(sco.s_score)FROM course cou LEFT JOIN score sco ON cou.c_id=sco.c_idGROUP BY cou.c_idORDER 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_idFROM scoreORDER 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

SELECTcou.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_idGROUP BY cou.c_id;

24

、查询学生平均成绩及其名次

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

25

、查询各科成绩前三名的记录

SELECT*FROM(SELECTc_id,s_id,s_score,IF(@prec=c_id,@rank:=@rank+1,@rank:=1)AS 名次,@prec:=c_idFROM score,(SELECT @rank:=0)r,(SELECT @prec:=-1)pORDER 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

SELECTc_name,COUNT(s_id)AS '学生数'FROM score sc LEFT JOIN course co ON co.c_id=sc.c_idGROUP 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 studentGROUP BY s_sex

28

、查询男生、女生人数

SELECT s_sex,COUNT(*) FROM studentGROUP 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 stuWHERE stu.s_name IN(SELECT stu1.s_nameFROM student stu1WHERE stu.s_id != stu1.s_id) GROUP BY stu.s_name

31

、查询1990年出生的学生名单

SELECTc_id,avg(s_score)FROM scoreGROUP BY c_idORDER 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

SELECTc_id,avg(s_score)FROM scoreGROUP BY c_idORDER 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

SELECTsc.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_idGROUP BY sc.s_id HAVING avg(s_score) >= 85

、查询课程名称为”数学”，且分数低于60的学生姓名和分数

SELECTco.c_name,st.s_name,sc.s_scoreFROM score sc LEFT JOIN course co ON sc.c_id=co.c_idLEFT JOIN student st ON sc.s_id=st.s_idWHERE co.c_name='数学' AND sc.s_score<60-- 嵌套查询SELECTst.s_name,t.s_scoreFROM 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；

SELECTst.s_name,co.c_name,sc.s_scoreFROM score sc LEFT JOIN course co ON sc.c_id=co.c_idLEFT 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；

SELECTstu.s_name,co.c_name,sc.s_scoreFROM score sc LEFT JOIN student stu ON stu.s_id=sc.s_idLEFT JOIN course co ON co.c_id=sc.c_idWHERE sc.s_score > 70

37

、查询不及格的课程

SELECTco.c_name,stu.s_name,sc.s_scoreFROM score sc LEFT JOIN student stu ON stu.s_id=sc.s_idLEFT JOIN course co ON co.c_id=sc.c_idWHERE 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；

SELECTs_id,s_nameFROM studentWHERE s_id IN(SELECTs_idFROM scoreWHERE c_id = '01' AND s_score > 80)

39

、求每门课程的学生人数

SELECTco.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_idGROUP 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

SELECTst.*,co.c_name,sc.s_scoreFROM score sc LEFT JOIN student st ON st.s_id=sc.s_idLEFT JOIN course co ON sc.c_id=co.c_idLEFT JOIN teacher te ON te.t_id=co.t_idWHERE te.t_name='张三'ORDER BY sc.s_score DESCLIMIT 1

、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

SELECTstu.s_id,sc.c_id,sc.s_scoreFROM student stuLEFT JOIN score sc ON stu.s_id=sc.s_idWHERE sc.s_id IN(SELECTsc1.s_idFROM score sc1LEFT JOIN score sc2 ON sc1.s_id=sc2.s_id AND sc1.c_id!=sc2.c_idWHERE 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

SELECTsc.*FROM score sc WHERE (SELECT COUNT(*) FROM score sc1WHERE sc.c_id=sc1.c_id AND sc.s_score<=sc1.s_score)<=2ORDER 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(SELECTsc.c_id,COUNT(sc.s_id)AS '选修人数'FROM score sc LEFT JOIN course co ON co.c_id=sc.c_idGROUP BY sc.c_idORDER 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

、检索至少选修两门课程的学生学号

SELECTsc.s_id,COUNT(sc.c_id)FROM score sc GROUP BY sc.s_idHAVING COUNT(sc.c_id)>=2

、查询选修了全部课程的学生信息

SELECT*FROM student stuWHERE stu.s_id IN( SELECTsc.s_idFROM score sc GROUP BY sc.s_idHAVING COUNT(sc.c_id)=3)

46

、查询各学生的年龄

SELECTs_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 stuWHERE stu.s_id IN( SELECTsc.s_idFROM score sc GROUP BY sc.s_idHAVING COUNT(sc.c_id)=3)

46