标签：练习题 01 C# SQL score MySQL SC where select
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select version();
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#`;
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;
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
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;
标签：练习题,
01,
C#,
SQL,
score,
MySQL,
SC,
where,
select
From： https://www.cnblogs.com/wandaren/p/17001253.html