数据库练习代码

-- 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
drop database if exists school;

create database school;

use school;

-- 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');
insert into Student values('09' , '王菊' , '1990-02-20' , '女');
insert into Student values('10' , '王菊' , '1990-02-20' , '男');
-- 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);
insert into Score values('06' , '02' , 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 s.s_id,s.c_id,s.s_score,st.* 
from Score s ,student st 
where 
st.s_id=s.s_id 
and c_id like '01' 
and s_score>(select s_score from Score where c_id like '02' and s_id=s.s_id);

-- 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 s.s_id,s.c_id,s.s_score,st.* 
from Score s ,student st 
where 
st.s_id=s.s_id 
and c_id like '01' 
and s_score<(select s_score from Score where c_id like '02' and s_id=s.s_id);

select * from 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 s.s_id,avg(s_score),s2.s_name from score s,student s2 where s.s_id=s2.s_id  group by s_id having avg(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
        -- (包括有成绩的和无成绩的)

select s2.s_id,if(avg(s_score) is null,0,avg(s_score)),s2.s_name 
from score s RIGHT join student s2 on s.s_id=s2.s_id  
group by s_id 
having 
if(avg(s_score) is null,0,avg(s_score))<60 

select * from student

-- 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 s.s_name ,count(sc.s_score) as '选课总数' ,sum(sc.s_score) as '成绩' from student s left join score sc on s.s_id = sc.s_id group by s.s_id

-- 6、查询"李"姓老师的数量 
select * 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 s.s_id from score s,student st where s.s_id=st.s_id  and c_id=(select c_id from Course where t_id=(select t_id from Teacher where t_name like '张三')
);
-- 8、查询没学过"张三"老师授课的同学的信息 
 select * from student where
 s_id not in(select s.s_id from 
 score s,student st where s.s_id=st.s_id  
 and c_id=(select c_id from Course 
 where t_id=(select t_id from Teacher where t_name like '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 * from student where s_id in(select s_id from Score where c_id in(01,02) group by s_id having count(s_id)=2
)

-- 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 * from student where s_id in(select s_id from score where c_id ='01') and s_id not in (select s_id from student where s_id 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 * from student where s_id not in (select s_id from score group by s_id having count(1)=(select count(1) from Course)
)
 

-- 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 s.s_id from score sc right join student s on s.s_id=sc.s_id where s.s_id !='01' and c_id in(select c_id from score where s_id='01') group by s.s_id
)

-- 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 * from Student where s_id in(select s.s_id from score sc right join student s on s.s_id=sc.s_id where s.s_id !='01' and c_id in(select c_id from score where s_id='01') group by s.s_id having count(s.s_id)=(select count(c_id) 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 s_name from student where
 s_id not in(select s.s_id from 
 score s,student st where s.s_id=st.s_id  
 and c_id=(select c_id from Course 
 where t_id=(select t_id from Teacher where t_name like '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 s.s_id,avg(s_score),s_name from score s ,student st where s.s_id =st.s_id and s_score<60 group by s.s_id having count(s.s_id)>=2v                       

-- 16、检索"01"课程分数小于60，按分数降序排列的学生信息

select st.*,s.* from score s,student st where s.s_id =st.s_id and s_score <60 and c_id ='01' order by 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 
s_id,
avg(s.s_score),
(select sc.s_score from score sc where sc.s_id=s.s_id and c_id =01 ) as o1,
(select sc.s_score from score sc where sc.s_id=s.s_id and c_id =02 ) as o2,
(select sc.s_score from score sc where sc.s_id=s.s_id and c_id =03 ) as o3
from score s group by s.s_id order by avg(s.s_score) 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 c_id, max(s_score),min(s_score),avg(s_score),
 ((select count(1) from score where s_score>=60 group by c_id having c_id=s.c_id)/count(1)) as 及格,
  ((select count(1) from score where s_score>=70 and s_score<=80 group by c_id having c_id=s.c_id)/count(1)) as 中等,
     ((select count(1) from score where s_score>=80 and s_score<=90 group by c_id having c_id=s.c_id)/count(1)) as 优良,
      ((select count(1) from score where s_score>=90 group by c_id having c_id=s.c_id)/count(1)) as 优秀
 from score s group by c_id 
 
-- 19、按各科成绩进行排序，并显示排名 

SELECT s_id,c_id, s_score,ROW_NUMBER() OVER (PARTITION BY c_id ORDER BY s_score DESC) ranking FROM score

SELECT c_id, s_score,ROW_NUMBER() OVER (ORDER BY s_score DESC) ranking FROM score group by c_id ,s_score

-- 20、查询学生的总成绩并进行排名
 
SELECT s_id,RANK() OVER(ORDER BY sum(s_score) DESC)FROM score group by s_id

-- 21、查询不同老师所教不同课程平均分从高到低显示 
 
 select avg(s_score),s.c_id,t_name from score s ,Course c ,Teacher t where c.c_id=s.c_id and c.t_id=t.t_id group by s.c_id order by avg(s_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 * from 
(SELECT s_id,c_id, s_score,ROW_NUMBER() OVER (PARTITION BY c_id ORDER BY s_score DESC) ranking FROM score) as r 
,student st
where r.ranking in(2,3) and st.s_id=r.s_id

-- 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 s.c_id ,
(select count(1) from score where c_id=s.c_id and s_score<60)/count(1) as '0-60',
(select count(1) from score where c_id=s.c_id and s_score>=60 and s_score<=70)/count(1) as '60-70',
(select count(1) from score where c_id=s.c_id and s_score>70 and s_score<=85)/count(1) as '70-85',
(select count(1) from score where c_id=s.c_id and s_score>85)/count(1) as '85-100'
from score s group by s.c_id
 

-- 24、查询学生平均成绩及其名次 
 
 select avg(s_score) from score group by s_id order by avg(s_score) desc
 
 
SELECT s_id,avg(s_score),RANK() OVER(ORDER BY avg(s_score) DESC) as '排名' FROM score group by s_id

 
-- 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 * from 
(SELECT s_id,c_id, s_score,ROW_NUMBER() OVER (PARTITION BY c_id ORDER BY s_score DESC) ranking FROM score) as r 
,student st
where r.ranking<=3  and st.s_id=r.s_id

-- 26、查询每门课程被选修的学生数 
 
 select count(c_id) ,c_id from 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 count(1) ,s.s_id,st.s_name from score s ,student st where s.s_id=st.s_id group by s.s_id having count(1)=2

-- 28、查询男生、女生人数 
 
 select count(1),s_sex 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 count(1),s_name,s_sex from student group by s_name ,s_sex

-- 31、查询1990年出生的学生名单

select * from student where year(s_birth)=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 avg(s_score),c_id from score group by c_id order by avg(s_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 s.s_id,avg(s_score),st.s_name from score s ,student st where s.s_id=st.s_id group by s.s_id  having avg(s_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 
 
 select * from Score where c_id=(select c_id from Course where c_name="数学") and s_score<60
 

-- 35、查询所有学生的课程及分数情况； 

select * from Score sc,student st ,Course c where sc.s_id=st.s_id  and sc.c_id=c.c_id

 
 -- 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 s_name,c_name,s_score from Score sc,student st ,Course c where sc.s_id=st.s_id  and sc.c_id=c.c_id and s_score>70

-- 37、查询不及格的课程
 
 select s_name,c_name,s_score from Score sc,student st ,Course c where sc.s_id=st.s_id  and sc.c_id=c.c_id and 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 s_name,s_score,sc.s_id from Score sc,student st  where sc.s_id=st.s_id  and sc.c_id and s_score>80

 
-- 39、求每门课程的学生人数 
 
 
 select count(1),c.c_name from score s ,Course c where s.c_id=c.c_id group by s.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   
  
        -- 查询最高分（可能有相同分数）
   
        -- 查询信息

select * from student where s_id=(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")) and s_score=(select max(s_score) from score where c_id=(select c_id from Course where t_id =(select t_id from Teacher where t_name="张三")))
)

-- 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 s_score from score group by s_score having count(1)>1

select * from score where s_score in(select s_score from score group by s_score having count(1)>1
)

-- 42、查询每门功成绩最好的前两名 
 

select * from (SELECT s_id,c_id, s_score,ROW_NUMBER() OVER (PARTITION BY c_id ORDER BY s_score DESC) ranking FROM score
) as s where s.ranking<=2

-- 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(1) from score group by c_id having count(1)>=5 order by count(1) desc ,c_id asc

-- 44、查询至少选修两门课程的学生学号 
   
     select s_id from score group by s_id
     

-- 45、查询选修了全部课程的学生信息 
     
select * from student where s_id in(select s_id from score group by s_id having count(1)=(select count(1) from Course )
)

-- 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 *, if(MONTH(CURRENT_DATE)<month(s_birth),year(CURRENT_DATE)-year(s_birth)-1,year(CURRENT_DATE)-year(s_birth)) from Student

select * from student
select FORMAT(now(),%m)
SELECT date_format('20209213','%y')

select year(CURRENT_DATE)-year('1990-01-01')
select MONTH(CURRENT_DATE)<month('1990-01-01')

select if(MONTH(CURRENT_DATE)<month('1990-01-01'),year(CURRENT_DATE)-year('1990-01-01')-1,year(CURRENT_DATE)-year('1990-12-01'))

-- 47、查询本周过生日的学生
 

-- 48、查询下周过生日的学生
 

-- 49、查询本月过生日的学生

select *, if(MONTH(CURRENT_DATE)<month(s_birth),year(CURRENT_DATE)-year(s_birth)-1,year(CURRENT_DATE)-year(s_birth)) from Student

select * from student where MONTH(CURRENT_DATE)=month(s_birth)
 

-- 50、查询下月过生日的学生
 select * from student where if(MONTH(CURRENT_DATE)+1>12,1,MONTH(CURRENT_DATE)+1)= MONTH(s_birth)