MySQL经典练习题及答案，常⽤SQL语句练习50题表名和字段
–1.学⽣表
Student(s_id,s_name,s_birth,s_sex) –学⽣编号，学⽣姓名, 出⽣年⽉，学⽣性别
–2.课程表
Course(c_id,c_name,t_id) – –课程编号, 课程名称, 教师编号
–3.教师表
Teacher(t_id,t_name) –教师编号，教师姓名
–4.成绩表
Score(s_id,c_id,s_score) –学⽣编号，课程编号，分数
测试数据
#–1.学⽣表
#Student(s_id,s_name,s_birth,s_sex) –学⽣编号，学⽣姓名, 出⽣年⽉，学⽣性别
CREATE TABLE `Student` (
`s_id` VARCHAR(20),
s_name VARCHAR(20) NOT NULL DEFAULT'',
s_brith VARCHAR(20) NOT NULL DEFAULT'',
s_sex VARCHAR(10) NOT NULL DEFAULT'',
PRIMARY KEY(s_id)
);
#–2.课程表
#Course(c_id,c_name,t_id) – –课程编号, 课程名称, 教师编号
create table Course(
c_id varchar(20),
c_name VARCHAR(20) not null DEFAULT'',
t_id VARCHAR(20) NOT NULL,
PRIMARY KEY(c_id)h5制作网站秀米
);
/*
–3.教师表
Teacher(t_id,t_name) –教师编号，教师姓名
*/
CREATE TABLE Teacher(
t_id VARCHAR(20),
t_name VARCHAR(20) NOT NULL DEFAULT'',
PRIMARY KEY(t_id)
);
/*
–4.成绩表
Score(s_id,c_id,s_score) –学⽣编号，课程编号，分数
*/
Create table Score(
s_id VARCHAR(20),
c_id VARCHAR(20) not null default'',
s_score INT(3),
primary key(`s_id`,`c_id`)
);
插⼊数据
#--插⼊学⽣表测试数据
#('01' , '赵雷' , '1990-01-01' , '男')
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');
sqlyog登录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);
练习题和sql语句
1、查询"01"课程⽐"02"课程成绩⾼的学⽣的信息及课程分数-- 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 score01,c.s_score as score02 FROM
student a
JOIN score b ON a.s_id=b.s_id and b.c_id='01'
LEFT JOIN score c on a.s_id=c.s_id and c.c_id='02' or c.c_id = NULL 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-- 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 01_score,c.s_score as 02_score from
student a left join score b on a.s_id=b.s_id and b.c_id='01'or b.c_id=NULL join 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 b.s_id,b.s_name,ROUND(AVG(a.s_score),2) as avg_score from
student b
join score a on b.s_id = a.s_id
GROUP BY b.s_id,b.s_name HAVING ROUND(AVG(a.s_score),2)>=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
-- (包括有成绩的和⽆成绩的)
select b.s_id,b.s_name,ROUND(AVG(a.s_score),2) as avg_score from
student b
left join score a on b.s_id = a.s_id
GROUP BY b.s_id,b.s_name HAVING ROUND(AVG(a.s_score),2)<60
union
select a.s_id,a.s_name,0as avg_score from
student a
开启安卓底部导航栏where a.s_id not in (
select distinct s_id from score);
-- 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) as sum_course,sum(b.s_score) as sum_score from
student a
left join score b on a.s_id=b.s_id
GROUP BY a.s_id,a.s_name;
-- 6、查询"李"姓⽼师的数量
select count(t_id) from teacher where t_name like'李%';
-- 7、查询学过"张三"⽼师授课的同学的信息
select a.*from
student a
皮尔森 代码整洁之道join score b on a.s_id=b.s_id where b.c_id in(
select c_id from course where t_id =(
select t_id from teacher where t_name ='张三'));
-- 8、查询没学过"张三"⽼师授课的同学的信息
select*from
student c
where c.s_id not in(
select a.s_id from student a join score b on a.s_id=b.s_id where b.c_id in(
select c_id from course where t_id =(
select t_id from teacher where 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 a.*from
student a,score b,score c
where a.s_id = b.s_id and a.s_id = c.s_id and b.c_id='01'and c.c_id='02';
-- 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 a.*from
student a
where a.s_id in (select s_id from score where c_id='01' ) and a.s_id not in(select s_id from score where c_id='02')
-- 11、查询没有学全所有课程的同学的信息
select s.*from
student s where s.s_id in(
select s_id from score where s_id not in(
select a.s_id from score a
join score b on a.s_id = b.s_id and b.c_id='02'
join score c on a.s_id = c.s_id and c.c_id='03'
where a.c_id='01'))
-- 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*from student where s_id in(
select distinct a.s_id from score a where a.c_id in(select a.c_id from score a where a.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 student a where a.s_id in(
select distinct s_id from score where s_id!='01'and c_id in(select c_id from score where s_id='01')
group by s_id
having count(1)=(select count(1) from 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 a.s_name from student a where a.s_id not in (
select s_id from score where c_id =
(select c_id from course where t_id =(
select t_id from teacher where t_name ='张三'))
group by s_id);
-- 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,a.s_name,ROUND(AVG(b.s_score)) from
student a
left join score b on a.s_id = b.s_id
where a.s_id in(
select s_id from score where s_score<60GROUP BY s_id having count(1)>=2)
GROUP BY a.s_id,a.s_name
-- 16、检索"01"课程分数⼩于60，按分数降序排列的学⽣信息
select a.*,b.c_id,b.s_score from
student a,score b
where a.s_id = b.s_id and b.c_id='01'and b.s_score<60ORDER BY b.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,(select s_score from score where s_id=a.s_id and c_id='01') as语⽂,
(select s_score from score where s_id=a.s_id and c_id='02') as数学,
(select s_score from score where s_id=a.s_id and c_id='03') as英语,
round(avg(s_score),2) as平均分from score a GROUP BY a.s_id ORDER BY平均分DESC;
-- 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,b.c_name,MAX(s_score),MIN(s_score),ROUND(AVG(s_score),2),
ROUND(100*(SUM(case when a.s_score>=60then1else0end)/SUM(case when a.s_score then1else0end)),2) as及格率,
ROUND(100*(SUM(case when a.s_score>=70and a.s_score<=80then1else0end)/SUM(case when a.s_score then1else0end)),2) as中等率, ROUND(100*(SUM(case when a.s_score>=80and a.s_score<=90then1else0end)/SUM(case when a.s_score then1else0end)),2) as优良率, ROUND(10
0*(SUM(case when a.s_score>=90then1else0end)/SUM(case when a.s_score then1else0end)),2) as优秀率
from score a left join 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(实现不完全)
-- mysql没有rank函数
select a.s_id,a.c_id,
@i:=@i+1as 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 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+1as 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 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+1as 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 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+1as 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 course a
left join score b on a.c_id=b.c_id
left join 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+1as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BETWEEN2AND3
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+1as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BETWEEN2AND3
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+1as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BETWEEN2AND3;
mysql查询面试题及答案-- 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 >85and s_score <=100then1else0end) as `85-100`,
ROUND(100*(SUM(case when s_score >85and s_score <=100then1else0end)/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 >70and s_score <=85then1else0end) as `70-85`,
ROUND(100*(SUM(case when s_score >70and s_score <=85then1else0end)/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 >60and s_score <=70then1else0end) as `60-70`,
ROUND(100*(SUM(case when s_score >60and s_score <=70then1else0end)/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 >=0and s_score <=60then1else0end) as `0-60`,
ROUND(100*(SUM(case when s_score >=0and s_score <=60then1else0end)/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+1as'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_sc
ore:=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)<3
ORDER BY a.c_id,a.s_score DESC
-- 26、查询每门课程被选修的学⽣数
select c_id,count(s_id) from score a 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 student where s_id in(
select s_id from 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) as⼈数from student GROUP BY s_sex
-- 29、查询名字中含有"风"字的学⽣信息
select*from student where s_name like'%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 student a JOIN
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.s_sex
-- 31、查询1990年出⽣的学⽣名单
select s_name from 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,ROUND(AVG(s_score),2) as avg_score from score GROUP BY c_id ORDER BY avg_score 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,b.s_name,ROUND(avg(a.s_score),2) as avg_score from score a
left join student b on a.s_id=b.s_id GROUP BY s_id HAVING avg_score>=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c++socket与c通讯
select a.s_name,b.s_score from score b LEFT JOIN student a on a.s_id=b.s_id where b.c_id=(
select c_id from course where 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 else0end) as'语⽂',
SUM(case c.c_name when'数学'then b.s_score else0end) as'数学',
SUM(case c.c_name when'英语'then b.s_score else0end) as'英语',
SUM(b.s_score) as'总分'
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
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,b.c_name,c.s_score from course b left join score c on b.c_id = c.c_id
left join student a on a.s_id=c.s_id where c.s_score>=70
-- 37、查询不及格的课程
select a.s_id,a.c_id,b.c_name,a.s_score from score a left join course b on a.c_id = b.c_id
where a.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,b.s_name from score a LEFT JOIN student b on a.s_id = b.s_id
where a.c_id ='01'and a.s_score>80
-- 39、求每门课程的学⽣⼈数
select count(*) from 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
-- 查询⽼师id
select c_id from course c,teacher d where c.t_id=d.t_id and d.t_name='张三'
-- 查询最⾼分（可能有相同分数）
select MAX(s_score) from score where c_id='02'
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