经典SQL练习题_MySQL

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1. select version();

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数据准备

1. -- 1.学生表
2. -- S# 学生编号,Sname 学生姓名,Sage 出生年月,Ssex 学生性别
3. CREATE TABLE `Student` (
4.   `S#` varchar(10) NOT NULL,
5.   `Sname` varchar(100) NOT NULL,
6.   `Sage` datetime NOT NULL,
7.   `Ssex` varchar(10) NOT NULL
8. ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;
10. insert into Student values('01' , '赵雷' , '1990-01-01' , '男');
11. insert into Student values('02' , '钱电' , '1990-12-21' , '男');
12. insert into Student values('03' , '孙风' , '1990-05-20' , '男');
13. insert into Student values('04' , '李云' , '1990-08-06' , '男');
14. insert into Student values('05' , '周梅' , '1991-12-01' , '女');
15. insert into Student values('06' , '吴兰' , '1992-03-01' , '女');
16. insert into Student values('07' , '郑竹' , '1989-07-01' , '女');
17. insert into Student values('08' , '王菊' , '1990-01-20' , '女');
19. -- 2.课程表
20. -- C# --课程编号,Cname 课程名称,T# 教师编号
21. CREATE TABLE `Course` (
22.   `C#` varchar(10) NOT NULL,
23.   `Cname` varchar(10) NOT NULL,
24.   `T#` varchar(10) NOT NULL
25. ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;
27. insert into Course values('01' , '语文' , '02');
28. insert into Course values('02' , '数学' , '01');
29. insert into Course values('03' , '英语' , '03');
31. -- 3.教师表
32. -- T# 教师编号,Tname 教师姓名
33. CREATE TABLE `Teacher` (
34.   `T#` varchar(10) NOT NULL,
35.   `Tname` varchar(10) NOT NULL
36. ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;
38. insert into Teacher values('01' , '张三');
39. insert into Teacher values('02' , '李四');
40. insert into Teacher values('03' , '王五');
42. -- 4.成绩表
43. -- S# 学生编号,C# 课程编号,score 分数
44. CREATE TABLE `SC` (
45.   `S#` varchar(10) NOT NULL,
46.   `C#` varchar(10) NOT NULL,
47.   `score` decimal(18,1) NOT NULL
48. ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;
50. insert into SC values('01' , '01' , 80);
51. insert into SC values('01' , '02' , 90);
52. insert into SC values('01' , '03' , 99);
53. insert into SC values('02' , '01' , 70);
54. insert into SC values('02' , '02' , 60);
55. insert into SC values('02' , '03' , 80);
56. insert into SC values('03' , '01' , 80);
57. insert into SC values('03' , '02' , 80);
58. insert into SC values('03' , '03' , 80);
59. insert into SC values('04' , '01' , 50);
60. insert into SC values('04' , '02' , 30);
61. insert into SC values('04' , '03' , 20);
62. insert into SC values('05' , '01' , 76);
63. insert into SC values('05' , '02' , 87);
64. insert into SC values('06' , '01' , 31);
65. insert into SC values('06' , '03' , 34);
66. insert into SC values('07' , '02' , 89);
67. insert into SC values('07' , '03' , 98);

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1. 查询" 01 "课程比" 02 "课程成绩高的学生的信息及课程分数

1. -- 自连接
2. SELECT s.`S#` ,s.`C#` ,s.score,s2.`C#` ,s2.score ,s3.Sname ,s3.Sage ,s3.Ssex  
3. from SC s ,SC s2,Student s3 where s.`C#` ='01' and s2.`C#` ='02'
4. and s.`S#` = s2.`S#`
5. and s.score > s2.score and s.`S#` = s3.`S#`;
6. -- 左连接
7. select A.*,B.`C#`,B.score,C.Sname ,C.Sage ,C.Ssex
8. from Student C ,(select * from SC where `C#`='01')A
9. left join(select * from SC where `C#`='02')B
10. on A.`S#`=B.`S#`
11. where A.score>B.score and C.`S#` = A.`S#`;

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1.1 查询同时存在" 01 "课程和" 02 "课程的情况

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

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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 )

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

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1.3 查询不存在" 01 "课程但存在" 02 "课程的情况

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

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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

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

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3. 查询在 SC 表存在成绩的学生信息

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

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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 )

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

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4.1 查有成绩的学生信息

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

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5. 查询「李」姓老师的数量

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

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6. 查询学过「张三」老师授课的同学的信息

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

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7. 查询没有学全所有课程的同学的信息

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

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10. 查询没学过"张三"老师讲授的任一门课程的学生姓名

1. select * from Student
2. where `S#` in(select distinct `S#` from SC
3.               where `C#` in(select `C#` from SC where `S#`='01'));

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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

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

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12. 检索" 01 "课程分数小于 60，按分数降序排列的学生信息

1. select * from Student
2. where `S#` not in(select `S#` from SC
3. where `C#` in(select c.`C#` from Course c
4. where c.`T#` in (SELECT t.`T#` from Teacher t where t.Tname='张三')));

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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

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

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15.1 按各科成绩进行排序，并显示排名， Score 重复时合并名次

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

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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

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

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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

1. select
2.         `C#` ,
3.         count(`S#`) as '选修人数',
4.         max(score) as '最高分',
5.         min(score) as '最低分',
6.         avg(score) as '平均分',
7.         concat( round( 100 * (sum( case  when score >= 60 then 1 else 0 end ) / count(score) ), 2 ), '%' )  as '及格率',
8.         concat( round( 100 * (sum( case  when score >= 70 and score < 80 then 1 else 0 end ) / count(score) ), 2 ), '%' )  as '中等率',
9.         concat( round( 100 * (sum( case  when score >= 80 and score < 90 then 1 else 0 end ) / count(score) ), 2 ), '%' )  as '优良率',
10.         concat( round( 100 * (sum( case  when score > 90 then 1 else 0 end ) / count(score) ), 2 ), '%' )  as '优秀率'
11. from
12.         SC
13. group by
14.         `C#`
15. order by
16.         选修人数 desc,
17.         `C#`;

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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

[code]selectb.Cname ,a.*from(selects.`C#` ,sum(case when score >=85 and score =85 and score =70 and score =70 and score =60 and score =60 and score =0 and score =0 and score a.score)