MySQL经典50道练习题

MySQL基础+JDBC编程教程：https://zhuanlan.zhihu.com/p/32651307
参考答案：
https://blog.csdn.net/dehu_zhou/article/details/52881587
https://blog.csdn.net/huaxiawudi/article/details/82288044
其中部分代码进行了改写，技巧：每次只写最简单的语句实现一部分功能，再根据功能进行嵌套。

• 1.学生表
  Student(S,Sname,Sage,Ssex) --S 学生编号,Sname 学生姓名,Sage 出生年月,Ssex 学生性别
• 2.课程表
  Course(C,Cname,T) --C --课程编号,Cname 课程名称,T 教师编号
• 3.教师表
  Teacher(T,Tname) --T 教师编号,Tname 教师姓名
• 4.成绩表
  SC(S,C,score) --S 学生编号,C 课程编号,score 分数

--创建测试数据
create table Student(
S varchar(10),
Sname varchar(10),
Sage datetime,
Ssex nvarchar(10)
) ;
 
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');
 
create table SC(
S varchar(10),
C varchar(10),
score decimal(18,1)
);
 
insert into SC values('01' , '01' , 80);
insert into SC values('01' , '02' , 90);
insert into SC values('01' , '03' , 99);
insert into SC values('02' , '01' , 70);
insert into SC values('02' , '02' , 60);
insert into SC values('02' , '03' , 80);
insert into SC values('03' , '01' , 80);
insert into SC values('03' , '02' , 80);
insert into SC values('03' , '03' , 80);
insert into SC values('04' , '01' , 50);
insert into SC values('04' , '02' , 30);
insert into SC values('04' , '03' , 20);
insert into SC values('05' , '01' , 76);
insert into SC values('05' , '02' , 87);
insert into SC values('06' , '01' , 31);
insert into SC values('06' , '03' , 34);
insert into SC values('07' , '02' , 89);
insert into SC values('07' , '03' , 98);

create table Course(
C varchar(10),
Cname varchar(10),
T varchar(10)
);
 
insert into Course values('01' , '语文' , '02');
insert into Course values('02' , '数学' , '01');
insert into Course values('03' , '英语' , '03');
 
create table Teacher(
T varchar(10),
Tname varchar(10)
);
 
insert into Teacher values('01' , '张三');
insert into Teacher values('02' , '李四');
insert into Teacher values('03' , '王五');

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 a.*
,b.score AS '01分数'
,c.score AS '02分数'
FROM student a
INNER JOIN sc b
ON a.s=b.s AND b.c='01'
INNER JOIN sc c
ON a.s=c.s AND c.c='02'
WHERE b.score > c.score ;

2、查询"01"课程比"02"课程成绩低的学生的信息及课程分数
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 a.s
,a.sname
,AVG(b.score) AS avgnum
FROM student a
INNER JOIN sc b
ON a.s=b.s
GROUP BY a.s,a.sname
HAVING AVG(b.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
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
6、查询"李"姓老师的数量

SELECT COUNT(1) FROM teacherWHERE tname LIKE '李%' ;

7、查询学过"张三"老师授课的同学的信息

SELECT a.*
FROM student a
INNER JOIN sc b
ON a.s=b.s
INNER JOIN course c
ON b.c=c.c
INNER JOIN teacher d
ON c.t=d.t
WHERE d.tname='张三'
GROUP BY 1,2,3,4 ;

8、查询没学过"张三"老师授课的同学的信息

SELECT a.*
FROM student a
LEFT JOIN sc b
ON a.s=b.s
WHERE NOT EXISTS(
              SELECT *
              FROM course aa
              INNER JOIN teacher b
              ON aa.t=b.t
              INNER JOIN sc c
              ON aa.c=c.c
              WHERE b.tname='张三'
              AND c.s=a.s
       )
GROUP BY 1,2,3,4 ;

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 a.*
FROM student a
INNER JOIN sc b
ON a.s=b.s AND b.c='01'
INNER JOIN sc c
ON a.s=c.s AND c.c='02' ;

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 *
from student a
left join sc b
on a.s=b.s and b.c='01'
left join sc c
on a.s=c.s and c.c='02'
where b.c='01' and c.c is null ;

11、查询没有学全所有课程的同学的信息

SELECT a.*
FROM student a
LEFT JOIN sc b
ON a.s=b.s
LEFT JOIN (SELECT COUNT(1) anumFROM course) c
ON 1=1
GROUP BY 1,2,3,4
HAVING MAX(c.anum)>COUNT(b.c) ;

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 a.*
FROM student a
INNER JOIN sc b
ON a.s=b.s
WHERE EXISTS(
    SELECT 1 FROM sc WHERE s='01' AND c=b.c
)
GROUP BY 1,2,3,4 ;

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
使用GROUP_CONCAT函数和GROUP BY

SELECT Student.* FROM Student WHERE
 S IN (
 SELECT S FROM 
 (SELECT t.S,GROUP_CONCAT(t.C) c_ids FROM 
 (SELECT S,C FROM SC) t GROUP BY S) a 
 WHERE a.S!='01' AND a.c_ids='01,02,03'
 );

14、查询没学过"张三"老师讲授的任一门课程的学生姓名

SELECT Sname FROM Student WHERE Student.S NOT IN 
( SELECT Student.S FROM 
Student LEFT JOIN SC ON Student.S=SC.S
 LEFT JOIN Course ON SC.C=Course.C 
 LEFT JOIN Teacher ON Course.T=Teacher.T 
 WHERE Teacher.Tname='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 a.s
       ,a.sname
       ,AVG(b.score)
FROM student a
INNER JOIN sc b
ON a.s=b.s
GROUP BY 1,2
HAVING SUM(CASE WHENb.score>=60 THEN 0 ELSE 1 END)>=2 ;

16、检索"01"课程分数小于60，按分数降序排列的学生信息

SELECT a.*
       ,b.score
FROM student a
INNER JOIN sc b
ON a.s=b.s
WHERE
  b.c='01'
  AND b.score < 60
ORDER BY b.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 a.*
       ,SUM(CASE WHEN b.c='01' THEN b.scoreELSE 0 END) AS s01
       ,SUM(CASE WHEN b.c='02' THEN b.scoreELSE 0 END) AS s02
       ,SUM(CASE WHEN b.c='03' THEN b.score ELSE0 END) AS s03
       ,AVG(CASE WHEN b.score IS NULL THEN 0 ELSE b.score END) avs
FROM student a
LEFT JOIN sc b
ON a.s=b.s
GROUP BY 1,2,3,4
ORDER BY avs 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 a.c
       ,a.cname
       ,MAX(b.score)
       ,MIN(b.score)
       ,AVG(b.score)
       ,SUM(CASE WHEN b.score>=60 THEN 1 ELSE 0 END)/COUNT(1)
       ,SUM(CASE WHEN b.score>=70 AND b.score<80 THEN 1 ELSE 0 END)/COUNT(1)
       ,SUM(CASE WHEN b.score>=80 AND b.score<90 THEN 1 ELSE 0 END)/COUNT(1)
       ,SUM(CASE WHEN b.score>=90 THEN 1 ELSE 0 END)/COUNT(1)
FROM course a
INNER JOIN sc b
ON a.c=b.c
GROUP BY 1,2 ;

19、按各科成绩进行排序，并显示排名

    SELECT a.*,b.score
    FROM course a
    INNER JOIN sc b
    ON a.c=b.c
    WHERE a.c='01'
    ORDER BY b.c,score DESC

20、查询学生的总成绩并进行排名

SELECT a.*
       ,COUNT(b.c)+1 asall
FROM sc a
LEFT JOIN sc b
ON a.c=b.c AND a.score < b.score
GROUP BY 1,2,3
ORDER BY a.c,asall ;

21、查询不同老师所教不同课程平均分从高到低显示

SELECT *,AVG(c.score) 
FROM teacher a INNER JOIN course b ON a.t=b.t 
INNER JOIN sc c ON b.c=c.c 
GROUP BY a.Tname 
ORDER BY AVG(c.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 a.*,b.cname,b.score
FROM student a
INNER JOIN (
       SELECT a.*
              ,c.cname
              ,COUNT(b.c)+1 AStp
       FROM sc a
       LEFT JOIN sc b
       ON a.c=b.c AND a.score<b.score
       LEFT JOIN course c
       ON a.c=c.c
       GROUP BY 1,2,3,4
       HAVING COUNT(b.c)+1 IN(2,3)
       ORDER BY a.c,tp)b
ON a.s=b.s ;

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 a.c
       ,a.cname
       ,SUM(CASE WHEN b.score<=100 AND b.score>85 THEN 1 ELSE 0 END) AS '[100-85]'
       ,SUM(CASE WHEN b.score<=85  AND b.score>70 THEN 1 ELSE 0 END) AS '[85-70]'
       ,SUM(CASE WHEN b.score<=70  AND b.score>60 THEN 1 ELSE 0 END) AS '[70-60]'
       ,SUM(CASE WHEN b.score<=60  AND b.score>0 THEN 1 ELSE 0 END) AS '[60-0]'   
       ,SUM(CASE WHEN b.score<=100 AND b.score>85 THEN 1 ELSE 0 END)/COUNT(1) AS '[100-85]%'
       ,SUM(CASE WHEN b.score<=85  AND b.score>70 THEN 1 ELSE 0 END)/COUNT(1) AS '[85-70]%'
       ,SUM(CASE WHEN b.score<=70  AND b.score>60 THEN 1 ELSE 0 END)/COUNT(1) AS '[70-60]%'
       ,SUM(CASE WHEN b.score<=60  AND b.score>0 THEN 1 ELSE 0 END)/COUNT(1) AS '[60-0]%'
FROM course a
INNER JOIN sc b
ON a.c=b.c
GROUP BY 1,2 ;

24、查询学生平均成绩及其名次
自己对自己左交，查看比自己分数高的有几个

SELECT a.*
       ,COUNT(b.s)+1
FROM (
       SELECT a.*,AVG(CASE WHEN b.score IS NULL THEN 0 ELSE b.scoreEND) AS ascore
       FROM student a
       LEFT JOIN sc b
       ON a.s=b.s
       GROUP BY 1,2,3,4
      )a
LEFT JOIN(
       SELECT a.*,AVG(CASE WHEN b.score IS NULL THEN 0 ELSE b.scoreEND) AS ascore
       FROM student a
       LEFT JOIN sc b
       ON a.s=b.s
       GROUP BY 1,2,3,4
      )b
ON a.ascore<b.ascore
GROUP BY 1,2,3,4,5 ;

25、查询各科成绩前三名的记录

SELECT a.*,COUNT(b.c)+1 AS ascore
FROM sc a
LEFT JOIN sc b
ON a.c=b.c AND a.score<b.score
GROUP BY 1,2,3
HAVING ascore<=3
ORDER BY a.c,ascore ;

26、查询每门课程被选修的学生数

SELECT a.*,COUNT(b.s) 
FROM course a 
LEFT JOIN sc b 
ON a.c=b.c 
GROUP BY 1,2,3;

27、查询出只有两门课程的全部学生的学号和姓名

SELECT a.*,COUNT(b.c)
FROM student a
LEFT JOIN sc b
ON a.s=b.s
GROUP BY 1,2,3,4
HAVING COUNT(b.c)=2 ;

--变量写法
SELECT q.S,total,@crank:=@crank+1 FROM(
 SELECT SC.S,SUM(sc.score) AS total 
 FROM SC GROUP BY SC.S ORDER BY total DESC) q;

28、查询男生、女生人数
29、查询名字中含有"风"字的学生信息
30、查询同名同性学生名单，并统计同名人数

SELECT sname
       ,ssex
       ,COUNT(1)
FROM student
GROUP BY 1,2
HAVING COUNT(1) > 1 ;

31、查询1990年出生的学生名单(注：Student表中Sage列的类型是datetime)

SELECT * FROM student WHERE YEAR(sage)=1990 ;

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

SELECT a.*,AVG(b.score) ascore FROM course a 
LEFT JOIN sc b ON a.c=b.c 
GROUP BY 1,2,3 
ORDER BY ascore DESC,a.c ASC;

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 a.*
       ,AVG(b.score) ascore
FROM student a
LEFT JOIN sc b
ON a.s=b.s
GROUP BY 1,2,3,4
HAVING ascore>=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 c.*
FROM course a
LEFT JOIN sc b
ON a.c=b.c
LEFT JOIN student c
ON b.s=c.s
WHERE a.cname='数学'
AND b.score < 60 ;

35、查询所有学生的课程及分数情况

SELECT *
FROM sc a
INNER JOIN student b
ON a.s=b.s
INNER JOIN course c
ON a.c=c.c ;

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 b.sname
       ,c.cname
       ,a.score
FROM sc a
INNER JOIN student b
ON a.s=b.s
INNER JOIN course c
ON a.c=c.c
WHERE a.score > 70 ;

37、查询不及格的课程
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 a.*
FROM student a
INNER JOIN sc b
ON a.s=b.s
WHERE b.c='01' AND b.score > 80 ;

39、求每门课程的学生人数
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 a.*,b.score
FROM student a
INNER JOIN sc b
ON a.s=b.s
INNER JOIN(
       SELECT c.c
              ,MAX(c.score) AS maxscore
       FROM teacher a
       INNER JOIN course b
       ON a.t=b.t
       INNER JOIN sc c
       ON b.c=c.c
       WHERE a.tname='张三'
       GROUP BY c)c
ON b.c=c.c AND b.score=c.maxscore ;

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 a.*
FROM sc a
LEFT JOIN sc b
ON a.s=b.s AND a.score=b.score AND a.c <> b.c
GROUP BY 1,2,3
HAVING COUNT(b.s) > 0 ;

42、查询每门功成绩最好的前两名
同19
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

SELECT a.c
       ,COUNT(1) AS pnum
FROM sc a
GROUP BY 1
HAVING pnum > 5
ORDER BY pnum DESC,a.c ;

44、检索至少选修两门课程的学生学号
45、查询选修了全部课程的学生信息
46、查询各学生的年龄

SELECT a.*,YEAR(CURDATE())-YEAR(a.sage)
FROM student a ;

47、查询本周过生日的学生

select *
from student 
where WEEKOFYEAR(student.Sage)=WEEKOFYEAR(CURDATE());

48、查询下周过生日的学生
49、查询本月过生日的学生

select *
from student 
where MONTH(student.Sage)=MONTH(CURDATE());

50、查询下月过生日的学生

select *
from student 
where MONTH(student.Sage)=MONTH(CURDATE())+1;