MYSQL练习题（45题）

建表语句

-- 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 a.* ,b.score 01课程成绩,c.score 02课程成绩
from student a ,sc b ,sc c
where a.sid=b.sid and a.sid=c.sid
and b.cid='01' and c.cid='02'
and b.score>c.score



2.查询学过「张三」老师授课的同学的信息

SELECT a.* FROM student a JOIN sc b on a.sid=b.sid where b.cid in(
SELECT cid from course where cid in(
SELECT tid from teacher where Tname='张三'))


3.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
-- 参考网友代码
SELECT s.*
FROM student s LEFT JOIN (
SELECT sid,GROUP_CONCAT(cid) gc
FROM sc
GROUP BY sid) gs ON s.sid = gs.sid
WHERE gs.gc = (
SELECT GROUP_CONCAT(cid)
FROM sc
WHERE sid =01) AND s.sid != 01;

　　

5.查询各科成绩最高分、最低分和平均分 
SELECT b.cname,max(score),min(score),avg(score)
from sc a LEFT JOIN course b on a.cid=b.cid 
GROUP BY a.cid,b.cname
6.查询各学生的总成绩，按总成绩降序排列 

SELECT sid ,sum(score) as 总成绩
from sc
GROUP BY sid
ORDER BY 总成绩 desc

7.查询每门课程被选修的学生数

select a.CId,b.cname,count(a.cid) from sc a LEFT JOIN course b on  a.cid=b.cid
GROUP BY a.cid,b.cname;

8.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 sc a JOIN student b on a.sid=b.sid
where cid in(
SELECT cid from course WHERE cname='数学')
and a.score<60

9.查询有不及格数据的课程名称
SELECT a.*,b.cname
from sc a left JOIN course b on a.cid=b.cid
where a.score<60

10.求每门课程选修的的学生人数
select a.CId,b.cname,count(a.cid) from sc a LEFT JOIN course b on  a.cid=b.cid
GROUP BY a.cid,b.cname;



11.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 a.*,b.score
from student a
left join sc b on a.sid=b.sid
where b.cid in 
(SELECT cid from course c,teacher d where c.tid=d.tid and d.tname= '张三')
and b.score in 
(select DISTINCT MAX(score) from sc where cid in( SELECT cid
FROM course e LEFT JOIN teacher f on e.tid=f.tid
where f.tname='张三'))

12.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 a.*,b.score
from student a
left join sc b on a.sid=b.sid
where b.cid in 
(SELECT cid from course c,teacher d where c.tid=d.tid and d.tname= '张三')
and b.score in 
(select MAX(score) from sc where cid in( SELECT cid
FROM course e LEFT JOIN teacher f on e.tid=f.tid
where f.tname='张三'))
13.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 DISTINCT a.*
from sc a,sc b where a.cid!=b.cid and a.score = b.score 

14.检索至少选修两门课程的学生学号
SELECT sid , count(*) c
FROM sc
GROUP BY sc.sId
HAVING c >=2
15.查询选修了全部课程的学生信息
SELECT * from student 
WHERE sid in 
(SELECT sid from sc GROUP BY sid HAVING count(*) =(SELECT count(*) from course ))

16.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 MONTH(NOW()) from student
SELECT year(now())-year(Sage)-1 年龄减一,student.* from student 
where MONTH(NOW())-month(sage)<0 and
day(NOW())-day(sage)<0


SELECT year(now())-year(Sage) 年龄减一,student.* from student 
where  
17.查询本周过生日的学生 

SELECT * from student where WEEK(DATE_FORMAT(now(),'%y%M%d'))=WEEK(sage)
18.查询下周过生日的学生
SELECT * from student where week(DATE_FORMAT(NOW(),'%y%m%d'))+1 =WEEK(sage);
19.查询教师所教课程且选修人数多于5人的教师姓名


SELECT a.tname
from teacher a where tid in (
SELECT tid from course where cid in
(SELECT cid from sc GROUP BY cid having  count(*)>5))


20 查询选修“语文”课程的男同学的成绩
SELECT a.score,b.sname
from sc a LEFT JOIN student b on a.sid =b.sid
where b.ssex='男' and cid in(SELECT cid from course where cname='语文')

　　

1.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 b.SId,b.Sname,AVG(a.score) avgscore from 
	student b 
	left join sc a on b.SId = a.SId
	GROUP BY b.SId,b.Sname
	HAVING avgscore >=60

 
 2.查询在 SC 表存在成绩的学生信息

 select * from student where sid in (select sid from sc)
 
3.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 a.SId,a.Sname,count(b.CId) 选课总数,sum(b.score) 课程的总成绩 
from 
	student a 
	left join sc b on a.SId=b.SId
	GROUP BY a.SId,a.Sname;
			

4.查询「李」姓老师的数量

SELECT count(*) 李姓老师的数量  from 
teacher
where Tname like '李%'

5.查询没有学全所有课程的同学的信息
select * from student join ( select count(cid) 选修课程数,sid from sc group by sid HAVING count(cid)<( select count(cid) from course)) t where student.SId=t.sid union select s.*, 0 选修课程数,sid from student s where sid not in (SELECT sid from sc);

6.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 s
where s.SId
in(
SELECT sc.SId
from sc 
WHERE sc.CId in(
SELECT sc2.CId from sc sc2 where sc2.SId='01')
)

7.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 c 
where c.SId not in(
select a.SId from student a join sc b on a.SId=b.SId where b.CId in(
select a.CId from course a join teacher b on a.TId = b.TId where Tname ='张三'));



8.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 * from (select avg(score) 平均成绩,sid from sc group by sid ) t1 , (select count(*) 不及格课程数,sid from sc where score< 60 group by sid HAVING count(*)>=2) t2 where t1.sid=t2.sid



9.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 join (select * from sc where score<60 and cid='01' order by score desc) t on student.sid=t.sid;
10.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 * from student s left join ( select sc.sid,sc.cid,sc.score, 平均成绩 from sc join (select avg(score) 平均成绩,sid from sc group by sid ) t on sc.SId= t.sid order by 平均成绩 desc ) t2 on s.sid=t2.sid
11.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 total, CONCAT(s1/total*100,"%") '0-59 占比' , CONCAT(s2/total*100,"%") '60-70 占比' , CONCAT(s3/total*100,"%") '71-85 占比' , CONCAT(s4/total*100,"%") '86-100 占比' from course c1, (select * from (select count(*) total ,CId from sc group by cid) t0 left join ( select count(*) 's1',CId c1 from sc where sc.score BETWEEN 0 and 59 group by cid
) t1 on t0.cid=t1.c1 left join ( select count(*) 's2',CId c2 from sc where sc.score BETWEEN 60 and 70 group by cid ) t2 on t0.cid=t2.c2 left join ( select count(*) 's3',CId c3 from sc where sc.score BETWEEN 71 and 85 group by cid ) t3 on t0.cid=t3.c3 left join ( select count(*) 's4',CId c4 from sc where sc.score BETWEEN 86 and 100 group by cid ) t4 on t0.cid=t4.c4 ) ts where c1.CId=ts.cid
12.查询各科成绩前三名的记录
select * from student join ( select sc.sid,sc.score,sc.cid from sc join ( select max(score) maxscore ,cid from sc GROUP BY cid ) t where sc.CId=t.cid and sc.score=t.maxscore) t2 on student.sid=t2.sid


13.查询出只选修两门课程的学生学号和姓名

	SELECT SId,Sname 
	from student where SId in(
				SELECT SId from sc 
				GROUP BY SId HAVING COUNT(CId)=2);

14.查询男生、女生人数 
SELECT Ssex,count(Ssex)
from student 
GROUP BY Ssex


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

16.查询同名同性学生名单，并统计同名人数
SELECT s1.Sname, count(*) 同名人数
from student s1
 JOIN student s2
on s1.SId != s2.SId and s1.Sname=s2.Sname
and s1.Ssex=s2.Ssex
GROUP BY s1.Sname;




17.查询 1990 年出生的学生名单

SELECT * from student 
where Sage like '1990%';
18.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 CId,avg(score) avgscore
from sc 
GROUP BY CId
order by avgscore desc, CId asc


19.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 sc.SId ,s.Sname,avg(score) avgscore
from sc 
LEFT JOIN student s on sc.SId=s.SId 
GROUP BY sc.SId,s.Sname
having avgscore>=85;


20.查询各学生的年龄，只按年份来算

SELECT year(now())-year(Sage),stu
.* from student
21.查询所有学生的课程及分数情况（存在学生没成绩，没选课的情况也要罗列出来）
SELECT * from student LEFT JOIN sc on stuednt.SId=sc.SId;
22.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 s.Sname, c.Cname,sc.score
FROM course c
LEFT JOIN sc on c.CId=sc.CId
LEFT JOIN student s on s.SId=sc.SId
where sc.score>=70;


23.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 * from student join ( select sid,score from sc where score>80 and cid='01') t on student.SId= t.sid
24.查询每门功成绩最好的前两名
SELECT sc.* from sc ,( select a.sid,a.cid from sc as a left join sc as b on a.cid = b.cid and a.score<b.score group by a.cid, a.sid having count(b.CId)<2) t where sc.sid=t.sid and sc.cid=t.cid order by sc.cid;
25.统计每门课程的学生选修人数（超过 5 人的课程才统计）。
select CId,count(*) as countS 
	from sc 
	GROUP BY CId HAVING countS>5 
	ORDER BY countS,CId ASC