mysql练习题

-- 
create database exercise;

-- 学生表 Student
create table Student(
	SId varchar(10),
	Sname varchar(10),
	Sage datetime,
	Ssex varchar(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('09' , '张三' , '2017-12-20' , '女');
insert into Student values('10' , '李四' , '2017-12-25' , '女');
insert into Student values('11' , '李四' , '2017-12-30' , '女');
insert into Student values('12' , '赵六' , '2017-01-01' , '女');
insert into Student values('13' , '孙七' , '2018-01-01' , '女');

-- 科目表 Course
create table Course(
	CId varchar(10),
	Cname nvarchar(10),
	TId 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');

-- 教师表 Teacher
create table Teacher(
	TId 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');


-- 成绩表 SC
create table SC(
	SId varchar(10),
	CId 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);

-- 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 *
from (select SId ,score from sc where sc.CId='01')as t1 , (select SId ,score from sc where sc.CId='02') as t2
where t1.SId=t2.SId
and   t1.score>t2.score;

-- 1.1 查询同时存在" 01 "课程和" 02 "课程的情况
select *
from (select SId ,score from sc where sc.CId='01')as t1 inner join  (select SId ,score from sc where sc.CId='02') as t2
on t1.SId=t2.SId;

-- 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 SId, score from sc where sc.CId='01') as t1 left join (select SId, score from sc where sc.CId='02') as t2
on t1.SId=t2.SId;

-- 1.3 查询不存在" 01 "课程但存在" 02 "课程的情况
select * from sc where sc.SId not in (select SId from sc where sc.CId = '01') and sc.CId='02';

-- 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 student.*,t1.avgscore
from student inner JOIN(
select sc.SId ,AVG(sc.score)as avgscore
from sc 
GROUP BY sc.SId
HAVING AVG(sc.score)>=60)as t1 on student.SId=t1.SId

-- 3. 查询在 SC 表存在成绩的学生信息
select * from Student where Student.SId in (select distinct(sc.SId) 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 student.SId, student.Sname, t1.count, t1.sum from student left join(
select SId, count(Score) as count, sum(score) as sum from sc group by sc.SId
) as t1 on student.SId=t1.SId;

-- 4.1 查有成绩的学生信息
select * from student where student.SId in (select distinct(SId) from sc);

-- 5. 查询「李」姓老师的数量
select * from teacher where teacher.Tname like "李%";

-- 6. 查询学过「张三」老师授课的同学的信息
select student.*
from teacher  ,course  ,student,sc
where teacher.Tname='张三'
and   teacher.TId=course.TId
and   course.CId=sc.CId
and   sc.SId=student.SId

-- 7. 查询没有学全所有课程的同学的信息
select student.* from student where student.SId in 
(select sc.SId from sc group by sc.SId having count(sc.score) < 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 distinct student.* from sc, student
where sc.CId in (select CId from sc where sc.SId = "01")
and sc.SId=student.SId;

-- 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 student.SId not in (
select t1.SId
from 
(select student.SId,t.CId
from student ,(select sc.CId from sc where sc.SId='01') as t )as t1 
left join sc on t1.SId=sc.SId and t1.CId=sc.CId
where sc.CId is null )
and student.SId !='01';

-- 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 student.SId not in 
(
select student.SId
from student left join sc on student.SId=sc.SId 
where EXISTS 
(select *
from teacher ,course
where teacher.Tname='张三'
and   teacher.TId=course.TId
and 	course.CId=sc.CId))


-- 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 course.CId,course.Cname,t1.*
from course LEFT JOIN (
select sc.CId,CONCAT(sum(case when sc.score>=85 and sc.score<=100 then 1 else 0 end )/count(*)*100,'%') as '[85-100]',
CONCAT(sum(case when sc.score>=70 and sc.score<85 then 1 else 0 end )/count(*)*100,'%') as '[70-85)',
CONCAT(sum(case when sc.score>=60 and sc.score<70 then 1 else 0 end )/count(*)*100,'%') as '[60-70)',
CONCAT(sum(case when sc.score>=0 and sc.score<60 then 1 else 0 end )/count(*)*100,'%') as '[0-60)'
from sc
GROUP BY sc.CId) as t1 on course.CId=t1.CId

-- 18. 查询各科成绩前三名的记录
select *
from sc  
where  (select count(*) from sc as a where sc.CId =a.CId and  sc.score <a.score )<3
ORDER BY CId asc,sc.score desc;

-- 19. 查询每门课程被选修的学生数
select sc.CId,count(*)
from sc 
GROUP BY sc.CId;


-- 21.查询男生、女生人数
select student.Ssex ,count(*) as 人数
from student 
GROUP BY student.Ssex;

-- 22. 查询名字中含有「风」字的学生信息
select *
from student 
where student.Sname like '%风%';

-- 23.查询同名同性学生名单，并统计同名人数
select *
from student LEFT JOIN (select Sname,Ssex,COUNT(*)同名人数 from Student group by Sname,Ssex) as t1
on student.Sname =t1.Sname and student.Ssex=t1.Ssex
where t1.同名人数>1;

-- 24.查询 1990 年出生的学生名单
select *
from student
where YEAR(student.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 sc.CId,AVG(sc.score)
from sc 
GROUP BY sc.CId
ORDER BY AVG(sc.score) desc ,sc.CId asc;

-- 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 student.SId,student.Sname,t1.avgscore
from student INNER JOIN 
(select sc.SId ,AVG(sc.score) as avgscore from sc GROUP BY sc.SId HAVING AVG(sc.score)>85) as t1 on 
student.SId=t1.SId;


-- 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 student.Sname ,t1.score
from student INNER JOIN  (select sc.SId,sc.score 
from sc,course
where sc.CId=course.CId
and   course.Cname='数学'
and   sc.score<60)as t1 on student.SId=t1.SId;


-- 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 student.SId,sc.CId,sc.score from Student
left join sc  on student.SId=sc.SId;

-- 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 student.Sname,course.Cname,sc.score
from student , sc  ,course
where sc.score>=70
and  student.SId=sc.SId
and sc.CId=course.CId;


-- 30.查询存在不及格的课程
select DISTINCT sc.CId
from sc
where sc.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 student.SId,student.Sname
from student ,sc
where sc.CId='01'
and  student.SId=sc.SId
and  sc.score>80;

-- 32. 求每门课程的学生人数
select sc.CId,count(*) as 学生人数
from sc
GROUP BY sc.CId;

-- 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 student.*,sc.score
from student ,course ,teacher ,sc
where course.CId=sc.CId
and course.TId=teacher.TId
and teacher.Tname='张三'
and student.SId =sc.SId
LIMIT 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 *
from sc as t1
where exists(select * from sc as t2 where t1.SId=t2.SId and t1.CId!=t2.CId and t1.score =t2.score );


-- 36.查询每门功成绩最好的前两名
select *
from sc as t1
where (select count(*) from sc as t2 where t1.CId=t2.CId and t2.score >t1.score)<2
ORDER BY t1.CId;

-- 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 sc.CId as 课程编号,count(*) as 选修人数
from sc 
GROUP BY sc.CId
HAVING count(*)>5;

-- 38.检索至少选修两门课程的学生学号
select DISTINCT t1.SId
from sc as t1 
where (select count(* )from sc where t1.SId=sc.SId)>=3;

-- 40.查询各学生的年龄，只按年份来算
select student.SId as 学生编号,student.Sname as 学生姓名,
TIMESTAMPDIFF(YEAR,student.Sage,CURDATE()) as 学生年龄
from student;

-- 42.查询本周过生日的学生
select *
from student 
where YEARWEEK(student.Sage)=YEARWEEK(CURDATE());

-- 43. 查询下周过生日的学生
select *
from student 
where YEARWEEK(student.Sage)=CONCAT(YEAR(CURDATE()),week(CURDATE())+1);

-- 44.查询本月过生日的学生
select *
from student 
where EXTRACT(YEAR_MONTH FROM student.Sage)=EXTRACT(YEAR_MONTH FROM CURDATE());

-- 45.查询下月过生日的学生
select *
from student 
where 
EXTRACT(YEAR_MONTH FROM student.Sage)=EXTRACT(YEAR_MONTH FROM DATE_ADD(CURDATE(),INTERVAL 1 MONTH));