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经典SQL练习题_MySQL

2022-12-23 分类：野生技术 阅读(215) 评论(0)

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select version();

image.png

数据准备

-- 1.学生表
-- S# 学生编号,Sname 学生姓名,Sage 出生年月,Ssex 学生性别
CREATE TABLE `Student` (
  `S#` varchar(10) NOT NULL,
  `Sname` varchar(100) NOT NULL,
  `Sage` datetime NOT NULL,
  `Ssex` varchar(10) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;

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 
-- C# --课程编号,Cname 课程名称,T# 教师编号
CREATE TABLE `Course` (
  `C#` varchar(10) NOT NULL,
  `Cname` varchar(10) NOT NULL,
  `T#` varchar(10) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;

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 
-- T# 教师编号,Tname 教师姓名
CREATE TABLE `Teacher` (
  `T#` varchar(10) NOT NULL,
  `Tname` varchar(10) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;

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 
-- S# 学生编号,C# 课程编号,score 分数
CREATE TABLE `SC` (
  `S#` varchar(10) NOT NULL,
  `C#` varchar(10) NOT NULL,
  `score` decimal(18,1) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;

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);

1. 查询\" 01 \"课程比\" 02 \"课程成绩高的学生的信息及课程分数

-- 自连接
SELECT s.`S#` ,s.`C#` ,s.score,s2.`C#` ,s2.score ,s3.Sname ,s3.Sage ,s3.Ssex  
from SC s ,SC s2,Student s3 where s.`C#` =\'01\' and s2.`C#` =\'02\'
and s.`S#` = s2.`S#` 
and s.score > s2.score and s.`S#` = s3.`S#`;
-- 左连接
select A.*,B.`C#`,B.score,C.Sname ,C.Sage ,C.Ssex 
from Student C ,(select * from SC where `C#`=\'01\')A 
left join(select * from SC where `C#`=\'02\')B 
on A.`S#`=B.`S#` 
where A.score>B.score and C.`S#` = A.`S#`;

image.png

1.1 查询同时存在\" 01 \"课程和\" 02 \"课程的情况

-- 自连接
SELECT * from SC s,SC s2  where s.`C#` =\'01\' and s2.`C#` =\'02\' and s.`S#` = s2.`S#`;
-- 左连接
SELECT * from (select * from SC where `C#`=\'01\')A 
left join (select * from SC where `C#`=\'02\')B on A.`S#`=B.`S#`
where B.`S#` is not null;

image.png

1.2 查询存在\" 01 \"课程但可能不存在\" 02 \"课程的情况(不存在时显示为 null )

SELECT * FROM (select * from SC where `C#`=\'01\') s
LEFT JOIN (select * from SC where `C#`=\'02\') s2
on s.`S#` = s2.`S#`;

1.3 查询不存在\" 01 \"课程但存在\" 02 \"课程的情况

SELECT * from SC s  where s.`C#` =\'02\' 
and s.`S#` not in(SELECT s2.`S#` FROM SC s2 where s2.`C#`=\'01\');

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

select A.`S#`,B.Sname,A.dc from(select `S#`,AVG(score)dc from SC group by `S#`)A
left join Student B on A.`S#`=B.`S#` where A.dc>=60;

3. 查询在 SC 表存在成绩的学生信息

select * from Student where `S#` in (select distinct `S#` from SC);

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(没成绩的显示为 null )

select B.`S#`,B.Sname,A.选课总数,A.总成绩 from
(select `S#`,COUNT(`C#`)选课总数,sum(score)总成绩 from SC group by `S#`)A
right join Student B on A.`S#`=B.`S#`;

4.1 查有成绩的学生信息

select B.`S#`,B.Sname,A.选课总数,A.总成绩 from
(select `S#`,COUNT(`C#`)选课总数,sum(score)总成绩 from SC group by `S#`)A
LEFT join Student B on A.`S#`=B.`S#`;

5. 查询「李」姓老师的数量

select COUNT(*)李姓老师数量 from Teacher where Tname like \'李%\';

6. 查询学过「张三」老师授课的同学的信息

select * from Student s 
where s.`S#` in ( SELECT s2.`S#` from SC s2 
                 WHERE s2.`C#` IN (SELECT c.`C#`  from Course c 
                  WHERE c.`T#` IN (SELECT t.`T#`  from Teacher t
                 WHERE t.Tname=\'张三\')));

7. 查询没有学全所有课程的同学的信息

select * from Student
where `S#` in(select `S#` from SC group by `S#` having COUNT(`C#`)<3);

8. 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 * from Student 
where `S#` in(select distinct `S#` from SC 
              where `C#` in(select `C#` from SC where `S#`=\'01\'));

9. 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 * from Student 
where `S#` in(select `S#` from SC where `C#` in(select distinct `C#` from SC where `S#`=\'01\') and `S#`<>\'01\'
group by `S#`
having COUNT(`C#`)>=3)

10. 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#` not in(select `S#` from SC 
where `C#` in(select c.`C#` from Course c 
where c.`T#` in (SELECT t.`T#` from Teacher t where t.Tname=\'张三\')));

11. 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,B.平均成绩 from Student A right join
(select `S#`,AVG(score)平均成绩 from SC where score<60 group by `S#` having COUNT(score)>=2)B
on A.`S#`=B.`S#`;

12. 检索\" 01 \"课程分数小于 60，按分数降序排列的学生信息

SELECT * FROM Student s2 
where s2.`S#` in(SELECT s.`S#` from SC s 
                 where s.`C#` =\'01\' and s.score <60 ORDER by score desc);

13. 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`S#`,max(case `C#` when \'01\' then score else 0 end)\'01\',
MAX(case `C#` when \'02\' then score else 0 end)\'02\',
MAX(case `C#` when \'03\' then score else 0 end)\'03\',AVG(score)平均分 from SC
group by `S#` order by 平均分 desc;

14. 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
  • 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 
	`C#` ,
	count(`S#`) as \'选修人数\', 
	max(score) as \'最高分\',
	min(score) as \'最低分\',
	avg(score) as \'平均分\',
	concat( round( 100 * (sum( case  when score >= 60 then 1 else 0 end ) / count(score) ), 2 ), \'%\' )  as \'及格率\',
	concat( round( 100 * (sum( case  when score >= 70 and score < 80 then 1 else 0 end ) / count(score) ), 2 ), \'%\' )  as \'中等率\',
	concat( round( 100 * (sum( case  when score >= 80 and score < 90 then 1 else 0 end ) / count(score) ), 2 ), \'%\' )  as \'优良率\',
	concat( round( 100 * (sum( case  when score > 90 then 1 else 0 end ) / count(score) ), 2 ), \'%\' )  as \'优秀率\'
from 
	SC 
group by 
	`C#` 
order by
	选修人数 desc,
	`C#`;

15. 按各科成绩进行排序，并显示排名， Score 重复时保留名次空缺

select *,RANK()over(order by score desc)排名 from SC;

15.1 按各科成绩进行排序，并显示排名， Score 重复时合并名次

select *,DENSE_RANK()over(order by score desc)排名 from SC;

16. 查询学生的总成绩，并进行排名，总分重复时保留名次空缺

select *,RANK()over(order by 总成绩 desc)排名 from(
select `S#`,SUM(score)总成绩 from SC group by `S#`)A;

16.1 查询学生的总成绩，并进行排名，总分重复时不保留名次空缺

select *,DENSE_RANK()over(order by 总成绩 desc)排名 from(
select `S#`,SUM(score)总成绩 from SC group by `S#`)A;

17. 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]，[60-0] 及所占百分比

select
b.Cname ,
a.*
from
(select
s.`C#` ,
sum(case when score >=85 and score <100 then 1 else 0 end) as \'[85_100]人数\' ,
concat(cast(100*sum(case when score >=85 and score <100 then 1 else 0 end)/COUNT(*) as decimal(4,2)) , \'%\') as \'[85_100]占比\',

sum(case when score >=70 and score <85 then 1 else 0 end) as \'[70_85]人数\' ,
concat(cast(100*sum(case when score >=70 and score <85 then 1 else 0 end)/COUNT(*) as decimal(4,2)) , \'%\') as \'[70_85]占比\',

sum(case when score >=60 and score <70 then 1 else 0 end) as \'[60_70]人数\' ,
concat(cast(100*sum(case when score >=60 and score <70 then 1 else 0 end)/COUNT(*) as decimal(4,2)) , \'%\') as \'[60_70]占比\',

sum(case when score >=0 and score <60 then 1 else 0 end) as \'[0_60]人数\' ,
concat(cast(100*sum(case when score >=0 and score <60 then 1 else 0 end)/COUNT(*) as decimal(4,2)) , \'%\') as \'[0_60]占比\'
from 
SC s
group by s.`C#`) a left join Course b on a.`C#` = b.`C#`;

18. 查询各科成绩前三名的记录

-- 方法一：
select * from SC a where (select COUNT(*)from SC where `C#`=a.`C#` and score>a.score)<3
order by a.`C#`,a.score desc;
-- 方法二：
select a.`S#`,a.`C#`,a.score from SC a 
left join SC b on a.`C#`=b.`C#` and a.score<b.score
group by a.`S#`,a.`C#`,a.score
having COUNT(b.`S#`)<3
order by a.`C#`,a.score desc;
-- 方法三：
-- select * from(select *,rank()over (partition by `C#` order by score desc)A from SC)B where B.A<=3;

19. 查询每门课程被选修的学生数

select `C#`,COUNT(`S#`)学生数 from SC group by `C#`

20. 查询出只选修两门课程的学生学号和姓名

select `S#`,Sname from Student 
where `S#` in(select `S#` from(select `S#`,COUNT(`C#`)课程数 from SC group by `S#`)A 
              where A.课程数=2);

21. 查询男生、女生人数

select Ssex,COUNT(Ssex)人数 from Student group by Ssex;

22. 查询名字中含有「风」字的学生信息

select * from Student where Sname like \'%风%\';

23. 查询同名同性学生名单，并统计同名人数

select A.*,B.同名人数 from Student A
left join (select Sname,Ssex,COUNT(*)同名人数 from Student group by Sname,Ssex)B 
on A.Sname=B.Sname and A.Ssex=B.Ssex
where B.同名人数>1;

24. 查询 1990 年出生的学生名单

select * from Student where YEAR(Sage)=1990;

25. 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#`,AVG(score)平均成绩 from SC group by `C#` order by 平均成绩 desc,`C#`;

26. 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.`S#`,A.Sname,B.平均成绩 from Student A
left join (select `S#`,AVG(score)平均成绩 from SC group by `S#`)B on A.`S#`=B.`S#`
where B.平均成绩>85;

27. 查询课程名称为「数学」，且分数低于 60 的学生姓名和分数

select B.Sname,A.score from(select * from SC 
                            where score<60 and `C#`=(select `C#` from Course 
                                                     where Cname=\'数学\'))A
left join Student B on A.`S#`=B.`S#`;

28. 查询所有学生的课程及分数情况（存在学生没成绩，没选课的情况）

select A.`S#`,B.`C#`,B.score from Student A left join SC B on A.`S#`=B.`S#`;

29. 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 A.Sname,D.Cname,D.score from 
(select B.*,C.Cname from(select * from SC where score>70)B left join Course C on B.`C#`=C.`C#`)D 
left join Student A on D.`S#`=A.`S#`;

30. 查询不及格的课程

SELECT * from Course c where c.`C#` in (select s.`C#` from SC s where score<60);

31. 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.`S#`,B.Sname from (select * from SC where score>80 and `C#`=\'01\')A
left join Student B on A.`S#`=B.`S#`;

32. 求每门课程的学生人数

  • 同19题

33. 成绩不重复，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 * from Student st 
where st.`S#` =(select s.`S#`  from SC s 
                where s.`C#`=(select c.`C#` from Course c 
                              where c.`T#`=(select t.`T#` from Teacher t 
                                            where t.Tname=\'张三\'))
order by s.score desc limit 1);

34. 成绩有重复的情况下，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 * from Student st 
where st.`S#` =(select `S#`  from(select *,DENSE_RANK()over (order by score desc)A 
from SC 
where `C#`=(select `C#` from Course 
            where `T#`=(select `T#` from Teacher where Tname=\'张三\')))B
where B.A=1);

35. 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 C.`S#`,max(C.`C#`)`C#`,max(C.score)score from SC C 
left join(select `S#`,avg(score)A from SC group by `S#`)B 
on C.`S#`=B.`S#`
where C.score=B.A
group by C.`S#`
having COUNT(0)=(select COUNT(0)from SC where `S#`=C.`S#`);

36. 查询每门功成绩最好的前两名

select * from
(select *,ROW_NUMBER()over(partition by `C#` order by score desc)A from SC)B
where B.A<3;

37. 统计每门课程的学生选修人数（超过 5 人的课程才统计）。

select `C#`,COUNT(`S#`)选修人数 from SC 
group by `C#`
having COUNT(`S#`)>5
order by 选修人数 desc,`C#`;

38. 检索至少选修两门课程的学生学号

select `S#` from SC
group by `S#`
having COUNT(`C#`)>=2;

39. 查询选修了全部课程的学生信息

select `S#` from SC 
group by `S#` 
having count(`C#`)=(select distinct COUNT(0)a from Course);

40. 查询各学生的年龄，只按年份来算

select s.Sname , year(now())-year(s.Sage) as age from Student s

41. 按照出生日期来算，当前月日 < 出生年月的月日则，年龄减一

select s.Sname , timestampdiff(year , s.Sage, now()) as age from Student s

42. 查询本周过生日的学生

select *
from Student s  
where WEEKOFYEAR(s.Sage)=WEEKOFYEAR(NOW());

43. 查询下周过生日的学生

select *
from Student s 
where WEEKOFYEAR(s.Sage)=WEEKOFYEAR(NOW())+1;

44. 查询本月过生日的学生

select *
from Student s 
where MONTH(s.Sage)=MONTH(current_date());

45. 查询下月过生日的学生

select *
from Student s 
where MONTH(s.Sage)=MONTH(current_date())+1;

来源：https://www.cnblogs.com/wandaren/p/17001253.html
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