经典SQL练习题_MySQL - ToB企服应用市场:ToB评测及商务社交产业平台

select version();

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-- 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);

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-- 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#`;

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-- 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;

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

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

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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;

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

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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#`;

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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#`;

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

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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')));

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

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

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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)

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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')));

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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#`;

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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);

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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;

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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#`;

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