50道MYSQL练习题及答案
50道MYSQL练习题目前题目好像有好几个题目版本，本版本前的前18题相较于后半部分难度明显会有提升，部分答案并非最优选择，仅供参考。同时部分答案涉及GROUP BY若提示sql_mode=only_full_group_by的错误，原因为MYSQL5.7及以上版本开启了 only_full_group_by 模式，导致原有的GROUP BY语句报错，具体解决方法本文不做赘述。
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
SC(SId,CId,score)
SId 学生编号,CId 课程编号,score 分数
建立数据表并插入数据
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);
练习题目
- 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 student RIGHT JOIN
(SELECT t1.sid,cldone_score,cldtwo_score FROM
(SELECT sid,score as cldone_score FROM sc WHERE CId='01') as t1,
(SELECT sid,score as cldtwo_score FROM sc WHERE CId='02') as t2
WHERE t1.cldone_score>t2.cldtwo_score AND t1.SId=t2.SId)r
ON student.SId=r.SId;
1.1 查询同时存在" 01 “课程和” 02 "课程的情况
SELECT * FROM(
(SELECT * FROM sc WHERE CId='01') AS t1,
(SELECT * FROM sc WHERE CId='02') AS t2
) WHERE 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 * FROM sc WHERE CId='01') AS t2
RIGHT JOIN
(SELECT * FROM sc WHERE CId='02') AS t1
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';
- 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.SId,Sname,ss FROM student,
(SELECT SId,AVG(score) as ss FROM sc
GROUP BY SId
HAVING AVG(score)>60
) r
WHERE student.SId=r.SId;
- 查询在 SC 表存在成绩的学生信息
SELECT student.* ,sc.score FROM
student,sc
WHERE student.SId=sc.SId;
- 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,Sname,r.sum,r.count FROM (
SELECT SID,SUM(score) as sum,COUNT(SId) as count
FROM sc
GROUP BY SId)r
RIGHT JOIN student
on student.SId = r.SID;
4.1 查有成绩的学生信息
SELECT * FROM student
WHERE EXISTS(
select sc.sid from sc
WHERE student.sid = sc.sid)
或
select * from student
where student.sid in (select sc.sid from sc);
- 查询「李」姓老师的数量
SELECT COUNT(TId) FROM
(SELECT * FROM teacher WHERE Tname LIKE '李%')r
GROUP BY r.Tid;
或
select count(*)
from teacher
where tname like '李%';
- 查询学过「张三」老师授课的同学的信息
SELECT student.* FROM sc,course,student,teacher
WHERE
student.SId=sc.SId
and course.TId=teacher.TId
and sc.CId=course.CId
AND Tname='张三';
- 查询没有学全所有课程的同学的信息
SELECT student.* FROM student
WHERE SId NOT in (
SELECT SId FROM sc
GROUP BY SId
HAVING COUNT(SId) =
(SELECT COUNT(CId) FROM course));
- 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 student.* FROM student
WHERE SId in(
SELECT SId FROM sc
WHERE CId in(
SELECT CId FROM sc WHERE SId='01'));
- 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 sid
from student
where not exists (select 1 from (select cid from sc where sid='01') b
where not exists(select 1 from sc
where sc.sid=student.sid and sc.cid=b.cid));
- 查询没学过"张三"老师讲授的任一门课程的学生姓名
SELECT student.* FROM student
WHERE SId not in(
SELECT SId FROM sc WHERE CId in(
SELECT course.CId FROM teacher,course
WHERE Tname='张三' AND course.TId=teacher.TId));
- 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 student.SId,student.Sname,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;
- 检索" 01 "课程分数小于 60，按分数降序排列的学生信息
SELECT student.* FROM student,(
SELECT SId FROM(SELECT * FROM sc
WHERE CId='01'
ORDER BY score)tem
WHERE tem.score<60)r
WHERE student.SId=r.SId;
或
select student.*, sc.score from student,sc
WHERE student.SId=sc.SId
AND score<60
AND CId='01'
ORDER BY score;
- 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 sc.*,t1.avg FROM sc RIGHT JOIN
(SELECT sid,AVG(score) as avg FROM sc
GROUP BY SId) as t1
on t1.SId=sc.SId
ORDER BY t1.avg DESC;
- 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 cid,
MAX(score) as max,
MIN(score) as min,
AVG(score) as avg,
COUNT(CId) as Count,
sum(CASE when sc.score>=60 THEN 1 ELSE 0 END)/COUNT(*) as jige,
sum(CASE WHEN sc.score>=70 and sc.score<80 THEN 1 ELSE 0 END)/COUNT(*) as zhongdeng,
sum(CASE WHEN sc.score>=80 AND sc.score<90 THEN 1 ELSE 0 END)/COUNT(*) as youliang,
SUM(CASE WHEN sc.score>=90 THEN 1 ELSE 0 END)/COUNT(*) as youxiu
FROM sc
GROUP BY CId
ORDER BY count DESC,sc.CId asc;
- 按各科成绩进行排序，并显示排名， Score 重复时保留名次空缺
• 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 a.cid,a.SId,a.score,COUNT(b.score)+1 as rank
FROM sc as a LEFT JOIN sc b
on a.score<b.score AND a.CId=b.CId
GROUP BY a.CId,a.SId,a.score
ORDER BY a.CId,rank asc;
- 查询学生的总成绩，并进行排名，总分重复时保留名次空缺
• 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
set @crank=0;
SELECT tmp.SId,tmp.total,@crank := @crank +1 as rank FROM
(SELECT sc.SId,SUM(sc.score) as total FROM sc
GROUP BY SId
ORDER BY total DESC)tmp;
- 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.cname, course.cid,
sum(case when sc.score<=100 and sc.score>85 then 1 else 0 end) as "[100-85]",
CONCAT(sum(case when sc.score<=100 and sc.score>85 then 1 else 0 end)/COUNT(*)*100,'%') as "[100-85]百分比",
sum(case when sc.score<=85 and sc.score>70 then 1 else 0 end) as "[85-70]",
CONCAT(sum(case when sc.score<=85 and sc.score>70 then 1 else 0 end)/COUNT(*)*100,'%') as "[85-70]百分比]" ,
sum(case when sc.score<=70 and sc.score>60 then 1 else 0 end) as "[70-60]",
CONCAT(sum(case when sc.score<=70 and sc.score>60 then 1 else 0 end)/COUNT(*)*100,'%') as "[70-60]百分比",
sum(case when sc.score<=60 and sc.score>0 then 1 else 0 end) as "[60-0]",
CONCAT(sum(case when sc.score<=60 and sc.score>0 then 1 else 0 end)/COUNT(*)*100,'%') as "[60-0]百分比"
from sc left join course
on sc.cid = course.cid
group by sc.cid;
- 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;
- 查询每门课程被选修的学生数
SELECT cid,COUNT(SId) as total FROM sc
GROUP BY CId;
- 查询出只选修两门课程的学生学号和姓名
SELECT student.SId,student.Sname,temp.total FROM student,(
SELECT sid,COUNT(CId) as total FROM sc
GROUP BY SId)temp
WHERE temp.total=2 AND student.SId=temp.Sid;
或
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);
- 查询男生、女生人数
select ssex, count(*) from student
group by ssex;
- 查询名字中含有「风」字的学生信息
SELECT * FROM student
WHERE Sname LIKE('%风%');
- 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;
- 查询 1990 年出生的学生名单
SELECT * FROM student
WHERE YEAR(Sage)=1990;
- 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 * FROM
(SELECT cid,AVG(score) as cidavg FROM sc
GROUP BY CId) as temp ORDER BY cidavg,cid asc;
- 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, AVG(sc.score) as aver from student, sc
where student.sid = sc.sid
group by sc.sid
having aver > 85;
- 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.cid,sc.score FROM course,sc,student
WHERE course.Cname='数学'
AND course.CId=sc.CId
AND student.SId=sc.SId
AND score<60;
- 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,student.Sname,sc.CId,score FROM student LEFT JOIN sc
on student.SId=sc.SId;
- 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.CId,course.Cname,sc.score
FROM sc,course,student
WHERE sc.score>70
AND sc.CId=course.CId
AND sc.SId=student.SId;
- 查询不及格的课程
SELECT CId,score FROM sc
WHERE sc.score<60
GROUP BY CId;
- 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 sc,student
WHERE CId='01'
AND sc.score>=80
AND sc.SId=student.SId;
- 求每门课程的学生人数
SELECT cid,count(SId) as count FROM sc
GROUP BY CId;
- 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,sc.CId FROM sc,student,teacher,course
WHERE teacher.Tname='张三'
AND teacher.TId=course.TId
AND course.CId=sc.CId
AND student.SId=sc.SId
HAVING max(sc.score);
- 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.tname = "张三"
AND teacher.tid = course.tid
AND sc.sid = student.sid
AND sc.cid = course.cid
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");
- 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 a.CId,a.SId,a.score FROM sc as a INNER JOIN sc as b
ON a.SId=b.SId
AND a.CId!=b.CId
AND a.score=b.score
GROUP BY CId,SId;
- 查询每门功成绩最好的前两名
select a.sid,a.cid,a.score 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
order by a.cid;
- 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(SId) FROM sc
GROUP BY CId
HAVING COUNT(SId)>5;
- 检索至少选修两门课程的学生学号
SELECT sid,COUNT(SId) as two FROM sc
GROUP BY SId
HAVING two>=2;
- 查询选修了全部课程的学生信息
select student.* from sc ,student
where sc.SId=student.SId
GROUP BY sc.SId
HAVING count(*) = (select DISTINCT count(*) from course );
- 查询各学生的年龄，只按年份来算
SELECT sid,YEAR(NOW())-YEAR(Sage) as age
FROM student;
- 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 student.SId as stu_id,student.Sname as stu_name,
TIMESTAMPDIFF(YEAR,student.Sage,CURDATE()) as age #时间差函数TIMESTAMPDIFF
from student;
- 查询本周过生日的学生
SELECT * FROM student
WHERE WEEKOFYEAR(Sage)=WEEKOFYEAR(CURDATE());
- 查询下周过生日的学生
select *
from student
where WEEKOFYEAR(student.Sage)=WEEKOFYEAR(CURDATE())+1;
- 查询本月过生日的学生
SELECT * FROM student
WHERE MONTH(Sage)=MONTH(CURDATE());
- 查询下月过生日的学生
SELECT * FROM student
WHERE MONTH(Sage)=MONTH(CURDATE())+1;