MySQL必学！！！（练习题50道精选）
一、 数据表介绍数据表介绍
–1.学生表
Student(SId,Sname,Sage,Ssex)
--SId 学生编号,Sname 学生姓名,Sage 出生年月,Ssex 学生性别
–2.课程表
Course(CId,Cname,TId)
--CId 课程编号,Cname 课程名称,TId 教师编号
–3.教师表
Teacher(TId,Tname)
--TId 教师编号,Tname 教师姓名
–4.成绩表
--SId 学生编号,CId 课程编号,score 分数
二、搭建情况
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' , '1990-12-20' , '男');
insert into Student values('04' , '李云' , '1990-12-06' , '男');
insert into Student values('05' , '周梅' , '1991-12-01' , '女');
insert into Student values('06' , '吴兰' , '1992-01-01' , '女');
insert into Student values('07' , '郑竹' , '1989-01-01' , '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' , '2012-06-06' , '女');
insert into Student values('12' , '赵六' , '2013-06-13' , '女');
insert into Student values('13' , '孙七' , '2014-06-01' , '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);
三、练习题
[*]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 t1.SId, class1, class2
-> from
-> (SELECT SId, score as class1 FROM SC WHERE SC.CId = '01') AS t1,
-> (SELECT SId, score as class2 FROM SC WHERE SC.CId = '02') AS t2
-> where t1.SId = t2.SId and t1.class1 > t2.class2
-> ) r
-> LEFT JOIN Student
-> ON Student.SId = r.SId;
https://i-blog.csdnimg.cn/blog_migrate/b18632fcb4ac7feba7715d8f02d15def.png
1.1 查询同时存在" 01 “课程和” 02 "课程的情况
select * from
(select * from SC where SC.CId = '01') as t1,
(select * from SC where SC.CId = '02') as t2
where t1.SId = t2.SId;
https://i-blog.csdnimg.cn/blog_migrate/2d9129c1d1f663573f9f97bc154c58bc.png
1.2 查询存在" 01 “课程但可能不存在” 02 "课程的情况(不存在时表现为 null )
select * from
-> (select * from SC where SC.CId = '01') as t1
-> left join
-> (select * from SC where SC.CId = '02') as t2
-> on t1.SId = t2.SId;
https://i-blog.csdnimg.cn/blog_migrate/13db98190d7cc5b81d1c04a28f1b7c6a.png
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';
https://i-blog.csdnimg.cn/blog_migrate/236872ce791acffb323a46a947faf74d.png
[*]查询平均成绩大于等于 60 分的同砚的学生编号和学生姓名和平均成绩
> select Student.SId, Student.Sname, r.ss from Student right join(
-> select SId, AVG(score) AS ss from SC
-> GROUP BY SId
-> HAVING AVG(score)> 60
-> )r on Student.SId = r.SId;
https://i-blog.csdnimg.cn/blog_migrate/3cb68484400f684119c9b6520c6ab02e.png
[*]查询在 SC 表存在成绩的学生信息
> select DISTINCT Student.*
-> from Student,SC
-> where Student.SId=SC.SId
-> ;
https://i-blog.csdnimg.cn/blog_migrate/1c9427579c9d95495aa55fd00b628155.png
[*]查询全部同砚的学生编号、学生姓名、选课总数、全部课程的总成绩(没成绩的表现为 null )
> select Student.sid, Student.sname,r.coursenumber,r.scoresum
-> from Student,
-> (select SC.sid, sum(SC.score) as scoresum, count(SC.cid) as coursenumber from SC
-> group by SC.sid)r
-> where Student.sid = r.sid;
https://i-blog.csdnimg.cn/blog_migrate/5c72e8fc97a6d3d78e221ce7e7c9f7e7.png
4.1查有成绩的学生信息
> select * from Student
-> where Student.sid in (select SC.sid from SC);
https://i-blog.csdnimg.cn/blog_migrate/8279bb18e32491918fc7eca5ad0f1145.png
[*]查询「李」姓老师的数目
> select count(*)
-> from Teacher
-> where tname like '李%';
https://i-blog.csdnimg.cn/blog_migrate/2f1ddb843d82437732d1e308ed02a26b.png
[*]查询学过「张三」老师授课的同砚的信息
> select Student.* from Student,Teacher,Course,SC
-> where
-> Student.sid = SC.sid
-> and Course.cid=SC.cid
-> and Course.tid =Teacher.tid
-> and tname = '张三';
https://i-blog.csdnimg.cn/blog_migrate/6517ad9c0f7e21548a8316f861603287.png
[*]查询没有学全全部课程的同砚的信息
> select * from Student
-> where Student.sid not in (
-> select SC.sid from SC
-> group by SC.sid
-> having count(SC.cid)= (select count(cid) from Course)
-> );
https://i-blog.csdnimg.cn/blog_migrate/93d3614d092a8845ee777951e9bd1663.png
[*]查询至少有一门课与学号为" 01 "的同砚所学雷同的同砚的信
> select * from Student
-> where Student.sid in (
-> select SC.sid from SC
-> where SC.cid in(
-> select SC.cid from SC
-> where SC.sid = '01'
-> )
-> );
https://i-blog.csdnimg.cn/blog_migrate/3ebcdee4073ab5f33a1068963013164d.png
[*]查询和" 01 "号的同砚学习的课程 完全雷同的其他同砚的信息
> SELECT a.SId, a.Sname, a.Sage, a.Ssex
-> FROM Student a, SC b
-> WHERE a.SId = b.SId AND b.CId IN (
-> SELECT CId
-> FROM SC
-> WHERE SId = '01'
-> ) AND a.SId <> '01';
https://i-blog.csdnimg.cn/blog_migrate/29798247ca2d2cdde52fb55fcfe7a77d.png
[*]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 SC.sid from SC,Course,Teacher
-> where
-> SC.cid = Course.cid
-> and Course.tid = Teacher.tid
-> and Teacher.tname= "张三");
https://i-blog.csdnimg.cn/blog_migrate/a11a5828042567a8a408fc0419df1ee7.png
[*]查询两门及其以上不合格课程的同砚的学号，姓名及其平均成绩
select Student.SId, Student.Sname,b.avg
-> from Student RIGHT JOIN
-> (select sid, AVG(score) as avg from SC
-> where sid in (
-> select sid from SC
-> where score<60
-> GROUP BY sid
-> HAVING count(score)>1)
-> GROUP BY sid) b on Student.sid=b.sid;
https://i-blog.csdnimg.cn/blog_migrate/8522baf316034e70e3bd826032f77a3b.png
[*]检索" 01 "课程分数小于 60，按分数降序排列的学生信息
> select Student.*, SC.score from Student, SC
-> where Student.sid = SC.sid
-> and SC.score < 60
-> and cid = "01"
-> ORDER BY SC.score DESC;
https://i-blog.csdnimg.cn/blog_migrate/4dab26978b41de20266ce0a6811fe56a.png
[*]按平均成绩从高到低表现全部学生的全部课程的成绩以及平均成绩
> select *from SC
-> left join (
-> select sid,avg(score) as avscore from SC
-> group by sid
-> )r
-> on SC.sid = r.sid
-> order by avscore desc;
https://i-blog.csdnimg.cn/blog_migrate/d48f8c72a76225b068e50ca79c975dbd.png
[*] 查询各科成绩最高分、最低分和平均分：
以如下情势表现：课程 ID，课程 name，最高分，最低分，平均分，合格率，中等率，优良率，良好率
合格为>=60，中等为：70-80，优良为：80-90，良好为：>=90
要求输出课程号和选修人数，查询结果按人数降序排列，若人数雷同，按课程号升序排列
[*] 按各科成绩举行排序，并表现排名， Score 重复时保存名次空缺
> select
-> SC.CId ,
-> max(SC.score)as 最高分,
-> min(SC.score)as 最低分,
-> AVG(SC.score)as 平均分,
-> count(*)as 选修人数,
-> sum(case when SC.score>=60 then 1 else 0 end )/count(*)as 及格率,
-> sum(case when SC.score>=70 and SC.score<80 then 1 else 0 end )/count(*)as 中等率,
-> sum(case when SC.score>=80 and SC.score<90 then 1 else 0 end )/count(*)as 优良率,
-> sum(case when SC.score>=90 then 1 else 0 end )/count(*)as 优秀率
-> from SC
-> GROUP BY SC.CId
-> ORDER BY count(*)DESC, SC.CId ASC
-> ;
https://i-blog.csdnimg.cn/blog_migrate/bce14ec51ee0668b550b0ea659fcaf46.png
[*]查询学生的总成绩，并举行排名，总分重复时保存名次空缺
[*] 统计各科成绩各分数段人数：课程编号，课程名称，，，， 及所占百分比
[*] 查询各科成绩前三名的纪录
> 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;
https://i-blog.csdnimg.cn/blog_migrate/89d075a428ae6d819c6a4a31ce0293cd.png
[*]查询每门课程被选修的学生数
> select cid, count(sid) from SC
-> group by cid;
https://i-blog.csdnimg.cn/blog_migrate/980e7eacac0eaa8288183003f4981e17.png
[*]查询出只选修两门课程的学生学号和姓名
> select Student.sid, Student.sname from Student
-> where Student.sid in
-> (select SC.sid from SC
-> group by SC.sid
-> having count(SC.cid)=2
-> );
https://i-blog.csdnimg.cn/blog_migrate/4ee459601b413c8664f99512f8d5c973.png
[*]查询男生、女生人数
> select ssex, count(*) from Student
-> group by ssex;
https://i-blog.csdnimg.cn/blog_migrate/6cbfdae87e0c3cef6bd632ce9307f056.png
[*]查询名字中含有「风」字的学生信息
> select *
-> from Student
-> where Student.Sname like '%风%'
-> ;
https://i-blog.csdnimg.cn/blog_migrate/42ef6b681244f5048a68a7c229617d28.png
[*]查询同名同性学生名单，并统计同名人数
> select sname, count(*) from Student
-> group by sname
-> having count(*)>1;
https://i-blog.csdnimg.cn/blog_migrate/3c8bbb0deecab38b99a7fecf4640cb3d.png
[*]查询 1990 年出生的学生名单
> select *
-> from Student
-> where YEAR(Student.Sage)=1990;
https://i-blog.csdnimg.cn/blog_migrate/c712d66aea9f76d15eec04d081112744.png
25. 查询每门课程的平均成绩，结果按平均成绩降序排列，平均成绩雷同时，按课程编号升序排列
[*] 查询平均成绩大于等于 85 的全部学生的学号、姓名和平均成绩
[*] 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, SC.score from Student, SC, Course
-> where Student.sid = SC.sid
-> and Course.cid = SC.cid
-> and Course.cname = "数学"
-> and SC.score < 60;
https://i-blog.csdnimg.cn/blog_migrate/58213d01072a508920b51dd0b9bf2393.png
[*]查询全部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.sname, cid, score from Student
left join SC
on Student.sid = SC.sid;
https://i-blog.csdnimg.cn/blog_migrate/b1f581dbd8f21a3d77b127e06c6bc4f3.png
[*]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,Course,SC
-> where SC.score>70
-> and Student.sid = SC.sid
-> and SC.cid = Course.cid;
https://i-blog.csdnimg.cn/blog_migrate/e0d601e5b51e50382558161ae7e7b74c.png
[*]查询不合格的课程
> select DISTINCT SC.CId
-> from SC
-> where SC.score <60;
https://i-blog.csdnimg.cn/blog_migrate/a915ef5175bdde843d774c6053687eae.png
[*]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 cid="01"
-> and score>=80
-> and Student.sid = SC.sid;
https://i-blog.csdnimg.cn/blog_migrate/411f12ed237b983b14d9ac5e7e82da36.png
[*]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;
https://i-blog.csdnimg.cn/blog_migrate/709e68f71774e271e6c857085e2142ba.png
[*]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
l> select Student.*, SC.score, SC.cid from Student, Teacher, Course,SC
-> where Teacher.tid = Course.tid
-> and SC.sid = Student.sid
-> and SC.cid = Course.cid
-> and Teacher.tname = "张三"
-> order by score desc
-> limit 1;
https://i-blog.csdnimg.cn/blog_migrate/f84e76f70027344b100c27c474a0a02e.png
[*]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 Student.*, SC.score, SC.cid from Student, Teacher, Course,SC
-> where Teacher.tid = Course.tid
-> and SC.sid = Student.sid
-> and SC.cid = Course.cid
-> and Teacher.tname = "张三"
-> and SC.score = (
-> select Max(SC.score)
-> from SC,Student, Teacher, Course
-> where Teacher.tid = Course.tid
-> and SC.sid = Student.sid
-> and SC.cid = Course.cid
-> and Teacher.tname = "张三"
-> );
https://i-blog.csdnimg.cn/blog_migrate/403035f2869de0804ecdd79d9a0b29fc.png
[*] 查询差别课程成绩雷同的学生的学生编号、课程编号、学生成绩
[*] 查询每门功成绩最好的前两名
[*]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, count(sid) as cc from SC
-> group by cid
-> having cc >5;
https://i-blog.csdnimg.cn/blog_migrate/9f68bac06ed2a91a299c5fda642f00dd.png
[*]检索至少选修两门课程的学生学号
> select sid, count(cid) as cc from SC
-> group by sid
-> having cc>=2;
https://i-blog.csdnimg.cn/blog_migrate/3273c76493359e76cdb3cd8b74daa6d1.png
[*]查询选修了全部课程的学生信息
[*]查询各学生的年岁，只按年份来算
SELECT s.SId, s.SName
FROM Student s
INNER JOIN SC sc ON s.SId = sc.SId
WHERE sc.Score > 80 AND sc.CId != '01';
https://i-blog.csdnimg.cn/blog_migrate/68a60f86e8168ef0a44b5702acef4b05.png
[*]按照出生日期来算，当前月日 < 出生年月的月日则，年岁减一
> select Student.SId as 学生编号,Student.Snameas学生姓名,
-> TIMESTAMPDIFF(YEAR,Student.Sage,CURDATE()) as 学生年龄
-> from Student
-> ;
https://i-blog.csdnimg.cn/blog_migrate/31f39b9d81d8b0464ec9bab748d2e8bb.png
[*]查询本周过生日的学生
select *
from Student
where WEEKOFYEAR(Student.Sage)=WEEKOFYEAR(CURDATE());
https://i-blog.csdnimg.cn/blog_migrate/df094c52dbc72233d892782b327cadb4.png
[*]查询下周过生日的学生
select *
from Student
where WEEKOFYEAR(Student.Sage)=WEEKOFYEAR(CURDATE())+1;
https://i-blog.csdnimg.cn/blog_migrate/13fae8a47edce5d4bd32900f0ee0b6b0.png
[*]查询本月过生日的学生
l> select *
-> from Student
-> where MONTH(Student.Sage)=MONTH(CURDATE());
https://i-blog.csdnimg.cn/blog_migrate/f93c0af477b8564342a9e86892063ee4.png
[*]查询下月过生日的学生
> select *
-> from Student
-> where MONTH(Student.Sage)=MONTH(CURDATE())+1;
https://i-blog.csdnimg.cn/blog_migrate/2b0f42b3f5df5062d0b17a5fb8de4da3.png
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