sql练习

一对多的情况下，不能使用not in .不然的话，剔除了本身，还有很多重复项

 

–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

--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

select a.* ,b.s_score as 01_score,c.s_score as 02_score 
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'
where b.s_score > c.s_score;

或者：

select a.*,b.s_score as 01_score,c.s_score as 02_score 
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' 
and b.s_score>c.s_score

 

#查询平均成绩小于60分的同学和没有成绩的的学生编号和学生姓名和平均成绩

select a.s_id,a.s_name,round(avg(b.s_score),2) as avg_score 
from student a
left join score b on a.s_id = b.s_id
group by a.s_id,a.s_name
having avg_score < 60 or avg_score is null

 

 

 

 

 

 

#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,round(avg(b.s_score),2) as avg_score 
from student a
left join score b on a.s_id = b.s_id
group by a.s_id,a.s_name
having avg_score >=60

 

#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 total_course,sum(b.s_score) as total_score
from student a
left join score b on a.s_id = b.s_id
group by a.s_id,a.s_name

 

#查询"李"姓老师的数量

#

 

 

select count(t.t_id) from teacher t
where t.t_name like '李%'

 

#查询学过"张三"老师授课的同学的信息

select a.*
from student a
inner 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'
    )
)

 

#

#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 a.c_id from course a 
        join teacher b on a.t_id = b.t_id 
        where t_name ='张三'
    )
);

 

#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
inner join score b on a.s_id = b.s_id
inner join score c on a.s_id = c.s_id
where b.c_id = '01'
and c.c_id = '02';

或者

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';

 

#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 * from student 
where s_id in (select s_id from score where c_id='01')
and s_id not in (select s_id from score where c_id='02')

 

#查询没有学全所有课程的同学的信息

select a.* from student a
left join score b on a.s_id = b.s_id
group by a.s_id
having count(b.s_id) < (select count(c_id) 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 a.* from student a
inner join score b on a.s_id = b.s_id
where b.c_id in (
    select c_id from score where s_id ='01'
)
group by a.s_id;

 

#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
inner join score b on a.s_id = b.s_id
where a.s_id <> '01'
group by b.s_id
having group_concat(b.c_id ORDER BY c_id) = 
    (
        select group_concat(c_id ORDER BY c_id) 
        from score where s_id = '01'
    );

 

#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 student where s_id not in (
    select distinct s_id from score where c_id in (
        select c_id from course where t_id = (select t_id from teacher where t_name ='张三')
    )
);

 

 #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),2) as avg_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 < 60 
    group by s_id 
    having count(s_id) >=2
)
group by a.s_id,a.s_name;

 

#检索"01"课程分数小于60，按分数降序排列的学生信息

select a.* from student a
inner join score b on a.s_id = b.s_id
where b.s_score < 60
and b.c_id = '01'
order by b.s_score desc;

 

#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;

 

 

 #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_name,max(b.s_score) as max_score,
    min(b.s_score) as min_score,
    round(avg(b.s_score),2) as avg_score ,
    round(100*sum(case when b.s_score >= 60 then 1 else 0 end)/sum(case when b.s_score then 1 else 0 end),2) as 及格率,
    round(100*sum(case when b.s_score >= 70 then 1 else 0 end)/sum(case when b.s_score then 1 else 0 end),2) as 中等率,
    round(100*sum(case when b.s_score >= 80 then 1 else 0 end)/sum(case when b.s_score then 1 else 0 end),2) as 优良率,
    round(100*sum(case when b.s_score >= 90 then 1 else 0 end)/sum(case when b.s_score then 1 else 0 end),2) as 优秀率
from course a
left join score b on a.c_id = b.c_id
group by a.c_id;

 

#查询学生的总成绩并进行排名

#

select * from (
    select a.s_id,sum(b.s_score) as total_score from student a
    left join score b on a.s_id = b.s_id
    group by a.s_id
)m
order by m.total_score desc

 

#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,a.t_name,b.c_id,round(avg(c.s_score),2) as avg_score 
from teacher a
left join course b on a.t_id = b.t_id
left join score c on b.c_id = c.c_id
group by a.t_id,b.c_id,a.t_name
order by avg_score desc;

 

#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' ORDER BY a.s_score DESC )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' ORDER BY a.s_score DESC 
)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' ORDER BY a.s_score DESC 
)c 
left join student d on c.s_id=d.s_id 
where 排名 BETWEEN 2 AND 3;

 

#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 a.c_id,a.c_name,
        sum(case when b.s_score > 85  and b.s_score <=100 then 1 else 0 end) as '85-100人数',
        round(100*sum(case when b.s_score > 85  and b.s_score <=100 then 1 else 0 end)/sum(case when b.s_score then 1 else 0 end),2) as '85-100比例',
        sum(case when b.s_score > 70  and b.s_score <=85 then 1 else 0 end) as '70-85人数',
    round(100*sum(case when b.s_score > 70  and b.s_score <=85 then 1 else 0 end)/sum(case when b.s_score then 1 else 0 end),2) as '70-85比例',
        sum(case when b.s_score > 60  and b.s_score <=70 then 1 else 0 end) as '60-70人数',
        round(100*sum(case when b.s_score > 60  and b.s_score <=70 then 1 else 0 end)/sum(case when b.s_score then 1 else 0 end),2) as '60-70比例',
        sum(case when b.s_score > 0  and b.s_score <=60 then 1 else 0 end) as '0-60人数',
    round(100*sum(case when b.s_score > 0  and b.s_score <=60 then 1 else 0 end)/sum(case when b.s_score then 1 else 0 end),2) as '0-60比例'
from course a
left join score b on a.c_id = b.c_id
group by a.c_id,a.c_name;

 

#查询学生平均成绩及其名次

select a.s_id,a.s_name,
        round(avg(b.s_score),2) as avg_score
from student a
left join score b on a.s_id = b.s_id
group by a.s_id,a.s_name
order by b.s_score desc ;

 

#查询每门课程被选修的学生数

select c.c_id,count(s.s_id) from course c
left join score s on c.c_id = s.c_id
group by c.c_id;

 

#查询出只有两门课程的全部学生的学号和姓名

 

转自：https://blog.csdn.net/fashion2014/article/details/78826299