MySQL常用练习50题（题目是网上的，有部分参考别人的代码）

MySQl练习题
–建表
–学生表
CREATE TABLE

Student

(

s_id

VARCHAR(20),

s_name

VARCHAR(20) NOT NULL DEFAULT ‘’,

s_birth

VARCHAR(20) NOT NULL DEFAULT ‘’,

s_sex

VARCHAR(10) NOT NULL DEFAULT ‘’,
PRIMARY KEY(

s_id

)
);
–课程表
CREATE TABLE

Course

(

c_id

VARCHAR(20),

c_name

VARCHAR(20) NOT NULL DEFAULT ‘’,

t_id

VARCHAR(20) NOT NULL,
PRIMARY KEY(

c_id

)
);
–教师表
CREATE TABLE

Teacher

(

t_id

VARCHAR(20),

t_name

VARCHAR(20) NOT NULL DEFAULT ‘’,
PRIMARY KEY(

t_id

)
);
–成绩表
CREATE TABLE

Score

(

s_id

VARCHAR(20),

c_id

VARCHAR(20),

s_score

INT(3),
PRIMARY KEY(

s_id

,

c_id

)
);
–插入学生表测试数据
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’);
–课程表测试数据
insert into Course values(‘01’ , ‘语文’ , ‘02’);
insert into Course values(‘02’ , ‘数学’ , ‘01’);
insert into Course values(‘03’ , ‘英语’ , ‘03’);

–教师表测试数据
insert into Teacher values(‘01’ , ‘张三’);
insert into Teacher values(‘02’ , ‘李四’);
insert into Teacher values(‘03’ , ‘王五’);

–成绩表测试数据
insert into Score values(‘01’ , ‘01’ , 80);
insert into Score values(‘01’ , ‘02’ , 90);
insert into Score values(‘01’ , ‘03’ , 99);
insert into Score values(‘02’ , ‘01’ , 70);
insert into Score values(‘02’ , ‘02’ , 60);
insert into Score values(‘02’ , ‘03’ , 80);
insert into Score values(‘03’ , ‘01’ , 80);
insert into Score values(‘03’ , ‘02’ , 80);
insert into Score values(‘03’ , ‘03’ , 80);
insert into Score values(‘04’ , ‘01’ , 50);
insert into Score values(‘04’ , ‘02’ , 30);
insert into Score values(‘04’ , ‘03’ , 20);
insert into Score values(‘05’ , ‘01’ , 76);
insert into Score values(‘05’ , ‘02’ , 87);
insert into Score values(‘06’ , ‘01’ , 31);
insert into Score values(‘06’ , ‘03’ , 34);
insert into Score values(‘07’ , ‘02’ , 89);
insert into Score values(‘07’ , ‘03’ , 98);

练习题
– 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.s_score as 01score, c.s_score as 02score from sys.student a
join sys.score b on a.s_id = b.s_id and b.c_id = ‘01’
join sys.score c on a.s_id = c.s_id and c.c_id = ‘02’
where b.s_score > c.s_score;

– 2、查询"01"课程比"02"课程成绩低的学生的信息及课程分数
select a.*, b.s_score as 01score, c.s_score as 02score from sys.student a
join sys.score b on a.s_id = b.s_id and b.c_id = ‘01’
join sys.score c on a.s_id = c.s_id and c.c_id = ‘02’
where b.s_score < c.s_score;

3、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_id, a.s_name, avg(b.s_score) from sys.student a
join sys.score b on a.s_id = b.s_id
group by a.s_id
having avg(b.s_score)>60;

– 4、查询平均成绩小于60分的同学的学生编号和学生姓名和平均成绩
select a.s_id, a.s_name, avg(b.s_score) from sys.student a
join sys.score b on a.s_id = b.s_id
group by a.s_id
having avg(b.s_score)<60;

– 5、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
select a.s_id, a.s_name, count(b.c_id), sum(b.s_score) from sys.student a
left join sys.score b on a.s_id = b.s_id
group by a.s_id;

– 6、查询"李"姓老师的数量
select count(b.t_name) from sys.teacher b where b.t_name like “李%”

– 7、查询学过"张三"老师授课的同学的信息
select a.* from sys.student a
left join sys.score b on a.s_id = b.s_id
left join sys.course c on b.c_id = c.c_id
left join sys.teacher d on c.t_id = d.t_id
where d.t_name = ‘张三’;

– 8、查询没学过"张三"老师授课的同学的信息
select a.* from sys.student a
where a.s_id not in (
select b.s_id from sys.student b join sys.score c on b.s_id = c.s_id
where c.c_id in (
select c_id from sys.course where t_id = (
select t_id from sys.teacher d where d.t_name = ‘张三’)));

– 9、查询学过编号为"01"并且也学过编号为"02"的课程的同学的信息
select c.* from sys.student c join sys.score d on c.s_id = d.s_id and d.c_id = 02 where c.s_id in (
select a.s_id from sys.student a join sys.score b on a.s_id = b.s_id where b.c_id = 01)

– 10、查询学过编号为"01"但是没有学过编号为"02"的课程的同学的信息
select c.* from sys.student c join sys.score d on c.s_id = d.s_id and d.c_id = 01 where c.s_id not in (
select a.s_id from sys.student a join sys.score b on a.s_id = b.s_id where b.c_id = 02);

– 11、查询没有学全所有课程的同学的信息
select e.* from sys.student e
where e.s_id not in (
select a.s_id from sys.Student a
left join sys.score b on a.s_id = b.s_id
left join sys.score c on a.s_id = c.s_id
left join sys.score d on a.s_id = d.s_id
where b.c_id = 01 and c.c_id = 02 and d.c_id = 03);

– 12、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 c.* from sys.student c
where c.s_id in (
select distinct(c.s_id) from sys.score c
where c.c_id in (
select a.c_id from sys.score a
where s_id = 01) and c.s_id <> 01);

– 13、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 a.* from sys.student a where a.s_id in(
select distinct s_id from sys.score where s_id!=‘01’ and c_id in(select c_id from sys.score where s_id=‘01’)
group by s_id
having count(1)=(select count(1) from sys.score where s_id=‘01’));

– 14、查询没学过"张三"老师讲授的任一门课程的学生姓名
select s_name from sys.student
where s_id not in(
select distinct(c.s_id) from sys.student c
left join sys.score d on c.s_id = d.s_id
where d.c_id = (
select c_id from sys.course a
left join sys.teacher b
on a.t_id = b.t_id
where b.t_name = ‘张三’));

– 15、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_id as 序号, a.s_name as 姓名, round(avg(b.s_score),2) as 平均分 from sys.student a
left join sys.score b on a.s_id = b.s_id
where a.s_id in(
select c.s_id from sys.score c
where c.s_score < 60
group by c.s_id
having count(c.s_id)>=2) group by a.s_id;

– 16、检索"01"课程分数小于60，按分数降序排列的学生信息
select b.* from sys.student b
where s_id in (
select a.s_id from sys.score a
where a.s_score<60 and a.c_id = 01
order by a.s_score desc);

– 17、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 a.s_id, round(avg(a.s_score),2),
(select s_score from sys.score where c_id = 01 and s_id = a.s_id) as ‘语文’,
(select s_score from sys.score where c_id = 02 and s_id = a.s_id) as ‘数学’,
(select s_score from sys.score where c_id = 03 and s_id = a.s_id) as ‘英语’
from sys.score a group by a.s_id

– 18.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
select a.c_id as ‘课程id’, b.c_name as ‘课程名称’, max(s_score) as ‘最高分’, min(s_score) as ‘最低分’, round(avg(s_score),2) as ‘平均分’,
ROUND(100*(SUM(case when a.s_s 20000 core>=60 then 1 else 0 end)/SUM(case when a.s_score then 1 else 0 end)),2) as 及格率,
ROUND(100*(SUM(case when a.s_score>=70 and a.s_score<=80 then 1 else 0 end)/SUM(case when a.s_score then 1 else 0 end)),2) as 中等率,
ROUND(100*(SUM(case when a.s_score>=80 and a.s_score<=90 then 1 else 0 end)/SUM(case when a.s_score then 1 else 0 end)),2) as 优良率,
ROUND(100*(SUM(case when a.s_score>=90 then 1 else 0 end)/SUM(case when a.s_score then 1 else 0 end)),2) as 优秀率
from sys.score a left join sys.course b on a.c_id = b.c_id GROUP BY a.c_id,b.c_name

– 19、按各科成绩进行排序，并显示排名
select a.s_id,a.c_id,
@i:=@i +1 as i保留排名,
@k:=(case when @score=a.s_score then @k else @i end) as rank不保留排名,
@score:=a.s_score as score
from (
select s_id,c_id,s_score from sys.score WHERE c_id=‘01’ GROUP BY s_id,c_id,s_score ORDER BY s_score DESC
)a,(select @k:=0,@i:=0,@score:=0)s
union
select a.s_id,a.c_id,
@i:=@i +1 as i,
@k:=(case when @score=a.s_score then @k else @i end) as rank,
@score:=a.s_score as score
from (
select s_id,c_id,s_score from sys.score WHERE c_id=‘02’ GROUP BY s_id,c_id,s_score ORDER BY s_score DESC
)a,(select @k:=0,@i:=0,@score:=0)s
union
select a.s_id,a.c_id,
@i:=@i +1 as i,
@k:=(case when @score=a.s_score then @k else @i end) as rank,
@score:=a.s_score as score
from (
select s_id,c_id,s_score from sys.score WHERE c_id=‘03’ GROUP BY s_id,c_id,s_score ORDER BY s_score DESC
)a,(select @k:=0,@i:=0,@score:=0)s

– 20、查询学生的总成绩并进行排名
select a.s_id,
@i:=@i+1 as i,
@k:=(case when @score=a.sum_score then @k else @i end) as rank,
@score:=a.sum_score as score
from (select s_id,SUM(s_score) as sum_score from score GROUP BY s_id ORDER BY sum_score DESC)a,
(select @k:=0,@i:=0,@score:=0)s

–21、查询不同老师所教不同课程平均分从高到低显示
select a.t_id,c.t_name,a.c_id,ROUND(avg(s_score),2) as avg_score from sys.course a
left join sys.score b on a.c_id=b.c_id
left join sys.teacher c on a.t_id=c.t_id
GROUP BY a.c_id,a.t_id,c.t_name ORDER BY avg_score DESC;

– 22、查询所有课程的成绩第2名到第3名的学生信息及该课程成绩
select d.,c.排名,c.s_score,c.c_id from (
select a.s_id,a.s_score,a.c_id,@i:=@i+1 as 排名 from score a,(select @i:=0)s where a.c_id=‘01’
)c
left join student d on c.s_id=d.s_id
where 排名 BETWEEN 2 AND 3
UNION
select d.,c.排名,c.s_score,c.c_id from (
select a.s_id,a.s_score,a.c_id,@j:=@j+1 as 排名 from score a,(select @j:=0)s where a.c_id=‘02’
)c
left join student d on c.s_id=d.s_id
where 排名 BETWEEN 2 AND 3
UNION
select d.*,c.排名,c.s_score,c.c_id from (
select a.s_id,a.s_score,a.c_id,@k:=@k+1 as 排名 from score a,(select @k:=0)s where a.c_id=‘03’
)c
left join student d on c.s_id=d.s_id
where 排名 BETWEEN 2 AND 3;

–23、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],[0-60]及所占百分比
select distinct f.c_name,a.c_id,b.

85-100

,b.百分比,c.

70-85

,c.百分比,d.

60-70

,d.百分比,e.

0-60

,e.百分比 from score a
left join (select c_id,SUM(case when s_score >85 and s_score <=100 then 1 else 0 end) as

85-100

,
ROUND(100*(SUM(case when s_score >85 and s_score <=100 then 1 else 0 end)/count()),2) as 百分比
from score GROUP BY c_id)b on a.c_id=b.c_id
left join (select c_id,SUM(case when s_score >70 and s_score <=85 then 1 else 0 end) as

70-85

,
ROUND(100(SUM(case when s_score >70 and s_score <=85 then 1 else 0 end)/count()),2) as 百分比
from score GROUP BY c_id)c on a.c_id=c.c_id
left join (select c_id,SUM(case when s_score >60 and s_score <=70 then 1 else 0 end) as

60-70

,
ROUND(100(SUM(case when s_score >60 and s_score <=70 then 1 else 0 end)/count()),2) as 百分比
from score GROUP BY c_id)d on a.c_id=d.c_id
left join (select c_id,SUM(case when s_score >=0 and s_score <=60 then 1 else 0 end) as

0-60

,
ROUND(100(SUM(case when s_score >=0 and s_score <=60 then 1 else 0 end)/count(*)),2) as 百分比
from score GROUP BY c_id)e on a.c_id=e.c_id
left join course f on a.c_id = f.c_id

–24、查询学生平均成绩及其名次
select a.s_id,
@i:=@i+1 as ‘不保留空缺排名’,
@k:=(case when @avg_score=a.avg_s then @k else @i end) as ‘保留空缺排名’,
@avg_score:=avg_s as ‘平均分’
from (select s_id,ROUND(AVG(s_score),2) as avg_s from score GROUP BY s_id)a,(select @avg_score:=0,@i:=0,@k:=0)b;

• 25、查询各科成绩前三名的记录
  – 1.选出b表比a表成绩大的所有组
  – 2.选出比当前id成绩大的 小于三个的
  select a.s_id,a.c_id,a.s_score from score a
  left join score b on a.c_id = b.c_id and a.s_score<b.s_score
  group by a.s_id,a.c_id,a.s_score HAVING COUNT(b.s_id)❤️
  ORDER BY a.c_id,a.s_score DESC

• 26、查询每门课程被选修的学生数
  select count(s_id), c_id from sys.score group by c_id

• 27、查询出只有两门课程的全部学生的学号和姓名
  select s_id, s_name from sys.student where s_id in(
  select s_id from sys.score group by s_id having count(c_id) = 2)

– 28、查询男生、女生人数
select s_sex, count(s_sex) from sys.student group by s_sex

– 29、查询名字中含有"风"字的学生信息
select * from sys.student where s_name = ‘%风’

– 30、查询同名同性学生名单，并统计同名人数
select a.s_name,a.s_sex,count(*) from sys.student a join
sys.student b on a.s_id <> b.s_id and a.s_name = b.s_name and a.s_sex = b.s_sex
group by a.s_name, a.

– 31、查询1990年出生的学生名单
select s_name from sys.student where s_birth like ‘1990%’

– 32、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_id, avg(s_score) as avg from sys.score group by c_id order by avg desc, c_id asc

– 33、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_id, a.s_name, avg(b.s_score) as avg from sys.student a left join sys.score b on a.s_id =b.s_id group by s_id, s_name having avg>=85

– 34、查询课程名称为"数学"，且分数低于60的学生姓名和分数
select a.s_name, b.s_score from sys.student a left join sys.score b on a.s_id = b.s_id left join sys.course c on b.c_id =c.c_id where c.c_name = ‘数学’ and b.s_score <60

– 35、查询所有学生的课程及分数情况；
select a.s_id,a.s_name,
sum(case c.c_name when ‘语文’ then b.s_score else 0 end) as ‘语文’,
SUM(case c.c_name when ‘数学’ then b.s_score else 0 end) as ‘数学’,
SUM(case c.c_name when ‘英语’ then b.s_score else 0 end) as ‘英语’,
SUM(b.s_score) as ‘总分’
from sys.student a left join sys.score b on a.s_id = b.s_id
left join sys.course c on b.c_id = c.c_id
GROUP BY a.s_id,a.s_name

– 36、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.s_name, c.c_name, b.s_score from sys.student a left join sys.score b on a.s_id =b.s_id left join sys.course c on b.c_id = c.c_id where b.s_score >70

– 37、查询不及格的课程
select a.s_id, a.s_name, b.s_score from sys.student a left join sys.score b on a.s_id = b.s_id where b.s_score <60

–38、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_id, a.s_name from sys.student a left join sys.score b on a.s_id = b.s_id where b.s_score >80 and b.c_id = 02

– 39、求每门课程的学生人数
select c_id, count(s_id) from sys.score group by c_id

– 40、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.s_score,b.c_id,c.c_name from student a
LEFT JOIN score b on a.s_id = b.s_id
LEFT JOIN course c on b.c_id=c.c_id
where b.c_id =(select c_id from course c,teacher d where c.t_id=d.t_id and d.t_name=‘张三’)
and b.s_score in (select MAX(s_score) from score where c_id=‘02’)

– 41、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 b.s_id, b.c_id, b.s_score from sys.score a, sys.score b
where a.c_id <> b.c_id and a.s_score = b.s_score

– 42、查询每门功成绩最好的前两名
select a.s_id,a.c_id,a.s_score from sys.score a
where (select COUNT(1) from sys.score b where b.c_id=a.c_id and b.s_score>=a.s_score)<=2 ORDER BY a.c_id

– 43、统计每门课程的学生选修人数（超过5人的课程才统计）。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_id, count() from sys.score group by c_id having count()>=5 order by count(*) desc, c_id asc

– 44、检索至少选修两门课程的学生学号
select s_id, count(s_id) from sys.score group by s_id having count(s_id)>=2

– 45、查询选修了全部课程的学生信息
select a.s_id, a.s_name from sys.student a where s_id in (
select s_id from sys.score group by s_id having count(s_id)=3)

–46、查询各学生的年龄
– 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_birth,(DATE_FORMAT(NOW(),’%Y’)-DATE_FORMAT(s_birth,’%Y’) -
(case when DATE_FORMAT(NOW(),’%m%d’)>DATE_FORMAT(s_birth,’%m%d’) then 0 else 1 end)) as age
from sys.student;

– 47、查询本周过生日的学生
select * from sys.student where WEEK(DATE_FORMAT(NOW(),’%Y%m%d’))=WEEK(s_birth)

– 48、查询下周过生日的学生
select * from sys.student where WEEK(DATE_FORMAT(NOW(),’%Y%m%d’))+1=WEEK(s_birth)

– 49、查询本月过生日的学生
select * from sys.student where month(DATE_FORMAT(NOW(),’%Y%m%d’))=month(s_birth)

– 50、查询下月过生日的学生
select * from sys.student where month(DATE_FORMAT(NOW(),’%Y%m%d’))+1=month(s_birth)