数据库练习

#创建数据库
create database EMS DEFAULT CHARSET 'utf8';
use EMS;
#创建学生表
create table Student(
s_id varchar(20) primary key,
s_name varchar(20) not null,
s_birth varchar(20) not null,
s_sex varchar(10) not null
);
#创建课程表
create table Course(
c_id varchar(20) primary key,
c_name varchar(20) not null,
t_id  varchar(20) not null
);
#创建教师表
create table Teacher(
t_id varchar(20) primary key,
t_name varchar(20) not null
);
#创建成绩表
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');
#插入课程表测试数据
insert into Course values('01' , '语文' , '02');
insert into Course values('02' , '数学' , '01');
insert into Course values('03' , '英语' , '03');
#插入教师表测试数据
insert into Teacher values('01' , '张三');
insert into Teacher values('02' , '李四');
insert into Teacher values('03' , '王五');
#插入成绩表测试数据
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);
#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.*,s1.s_score 01score,s2.s_score 02score 
from Score s1,Score s2,Student s
where s.s_id=s1.s_id and
s1.s_id=s2.s_id and
s1.c_id='01' and 
s2.c_id='02' and 
s1.s_score >s2.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 s.*,s1.s_score 01score,s2.s_score 02score 
from Score s1,Score s2,Student s
where s.s_id=s1.s_id and
s1.s_id=s2.s_id and
s1.c_id='01' and 
s2.c_id='02' and 
s1.s_score <s2.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 Student.s_id,s_name,avg(s_score)
from Score,Student
where Score.s_id=Student.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
select Student.s_id,s_name,avg(s_score) avg
from Score,Student
where Score.s_id=Student.s_id
group by s_id
having avg(s_score)<60
union
select a.s_id,a.s_name,0 as avg from 
    Student a 
    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 Student.s_id,s_name,count(c_id) coursesum,sum(s_score) sum
from Student,Score
where Student.s_id=Score.s_id 
group by s_id
union
select a.s_id,a.s_name,0 coursesum,0 sum from 
    Student a 
    where a.s_id not in (
                select distinct s_id from Score);
#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 s.* from Student s,Score,Teacher,Course
where s.s_id=Score.s_id and 
Score.c_id=Course.c_id and
Course.t_id=Teacher.t_id and
Teacher.t_name='张三';
# 8、查询没学过"张三"老师授课的同学的信息 
select s.* from Student s
where s_id not in
(select s_id from
Score where c_id in
(select c_id from 
Course where t_id in
(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 s.* from Student s,Score a,Score b
where s.s_id=a.s_id and
a.s_id=b.s_id and
a.c_id='01' and 
b.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 s.* from Student s
where s.s_id in (select s_id from score where c_id='01') and
s.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 
left outer join Score s1 on s1.s_id=s.s_id
group by s.s_id having count(s1.c_id)<(select count(*) 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  distinct Student.* from Student,Score
where Student.s_id in(select  s_id from Score where c_id in
(select c_id from Score where s_id='01')and Student.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 Student.* from Student 
where s_id in(select distinct Score.s_id 
from Score where s_id <> '01' and
 Score.c_id in (select distinct c_id from
 Score where s_id = '01')group by Score.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 s_name from Student where Student.s_id not in
(select distinct Score.s_id from 
Score , Course , Teacher where 
Score.c_id = Course.c_id and 
Course.T_id = Teacher.t_id and
Teacher.t_name = '张三')
order by Student.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 Student.s_id,s_name,avg(s_score) avg from Student,Score
where Student.s_id=Score.s_id and Student.s_id in (select s_id from Score where s_score < 60 group by s_id having count(1) >= 2)
group by Student.s_id,Student.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 Student.* ,c_id,s_score from Student,Score
where Student.s_id=Score.s_id and
 c_id='01' and s_score<60 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 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 课程号,b.c_name 课程名,MAX(s_score) 最高分,MIN(s_score) 最低分,ROUND(AVG(s_score),2) 平均成绩,
    ROUND(100*(SUM(case when a.s_score>=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 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
select  a.s_id ,a.c_id, a.s_score, count( distinct b.s_score)+1 as rank
from Score a left join  Score b  on a.c_id=b.c_id  and a.s_score<b.s_score
group by a.c_id, a.s_id
order by a.c_id, a.s_score desc;
#20、查询学生的总成绩并进行排名
set @rank = 0;
select a.* , @rank := @rank + 1 from 
(select Student.*,sum(s_score) sum_score  from Score sc 
left join Student on(sc.s_id=Student.s_id)
group by s_id
order by sum_score desc) a;
# 21、查询不同老师所教不同课程平均分从高到低显示
select Course.t_id,t_name,Course.c_id,c_name,avg(s_score) avg_score from Course
left join Score on(Course.c_id=Score.c_id)
left join Teacher on(Course.t_id=Teacher.t_id)
group by t_id
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
#分数相同，名次视为相同
select s.* from (select distinct Student.*,a.c_id, a.s_score, count( distinct b.s_score)+1 as rank
from Score a  left join  Score b  on a.c_id=b.c_id  and a.s_score<b.s_score
left join Student on(a.s_id=Student.s_id)
group by a.c_id, a.s_id
order by a.c_id, a.s_score desc) s
where s.rank 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 c.c_id,c.c_name 
,((SELECT COUNT(1)  FROM Score sc WHERE sc.c_id=c.c_id AND sc.s_score<=100 AND sc.s_score>80)/(SELECT COUNT(1) FROM score sc WHERE sc.c_id=c.c_id ))*100 '100-85所占百分比'
, (SELECT COUNT(1)  FROM Score sc WHERE sc.c_id=c.c_id AND sc.s_score<=100 AND sc.s_score>80)'[100-85]人数'
,((SELECT COUNT(1) FROM Score sc WHERE sc.c_id=c.c_id AND sc.s_score<=85 AND sc.s_score>70)/(SELECT COUNT(1) FROM score sc WHERE sc.c_id=c.c_id ))*100 '85-70所占百分比'
,(SELECT COUNT(1) FROM Score sc WHERE sc.c_id=c.c_id AND sc.s_score<=85 AND sc.s_score>70) '[85-70]人数'
,((SELECT COUNT(1) FROM Score sc WHERE sc.c_id=c.c_id AND sc.s_score<=70 AND sc.s_score>60)/(SELECT COUNT(1) FROM score sc WHERE sc.c_id=c.c_id ))*100 '70-60所占百分比'
,(SELECT COUNT(1) FROM Score sc WHERE sc.c_id=c.c_id AND sc.s_score<=70 AND sc.s_score>60) '[0-60]人数'
,((SELECT COUNT(1) FROM Score sc WHERE sc.c_id=c.c_id AND sc.s_score<=60 AND sc.s_score>=0)/(SELECT COUNT(1) FROM score sc WHERE sc.c_id=c.c_id ))*100 '60-0所占百分比'
,(SELECT COUNT(1) FROM Score sc WHERE sc.c_id=c.c_id AND sc.s_score<=60 AND sc.s_score>=0) '[0-60]人数'
FROM Course c ORDER BY c.c_id;
# 24、查询学生平均成绩及其名次 
select s.*,
    (select 1+COUNT(avg_score)
    from (select s_id,AVG(s_score) as avg_score
          from Score 
          group by s_id) as t1
    where avg_score > t2.avg_score) as rank,avg_score
from (select s_id,AVG(s_score) as avg_score
      from Score 
      group by s_id) as t2
      left join Student s on(s.s_id=t2.s_id)
order by avg_score desc ;
#25、查询各科成绩前三名的记录
select s.* from (select distinct Student.*,a.c_id, a.s_score, count( distinct b.s_score)+1 as rank
from Score a  left join  Score b  on a.c_id=b.c_id  and a.s_score<b.s_score
left join Student on(a.s_id=Student.s_id)
group by a.c_id, a.s_id
order by a.c_id, a.s_score desc) s
where s.rank between 1 and 3;
#26、查询每门课程被选修的学生数 
select c_id,count(s_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 Student.s_id,s_name from Student,Score
where Student.s_id=Score.s_id 
group by s_id
having count(c_id)=2;
#28、查询男生、女生人数 
select s_sex,count(s_sex) 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 s1.S_name,s1.s_sex,count(*) from Student s1,Student s2
where s1.s_name=s2.s_name and s1.s_sex=s2.s_sex and s1.s_id!=s2.s_id;
#31、查询1990年出生的学生名单
select s_name,s_birth 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 Score.s_id,Student.s_name,ROUND(avg(s_score),2) as avg_score
from Score 
left join Student on Score.s_id=Student.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
select s_name,s_score from Course,Student,Score
where Course.c_name='数学' and 
Course.c_id=Score.c_id and 
Score.s_id=Student.s_id
group by Student.s_id 
having 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 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 a.c_id,b.c_name,count(s_id) '学生人数' from Score a 
left join Course b on a.c_id=b.c_id
group by a.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 s.*, s_score,Score.c_id,Course.c_name from Student s,Score,Teacher,Course
where s.s_id=Score.s_id and 
Score.c_id=Course.c_id and
Course.t_id=Teacher.t_id and
Teacher.t_name='张三'and 
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 Score a,Score b 
where a.c_id != b.c_id and 
a.s_score = b.s_score;    
# 42、查询每门功课成绩最好的前两名   
select a.s_id,a.c_id,a.s_score from Score a
where (select count(s_id) from 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(*) as total from Score 
group by c_id 
having total>5 
order by total 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) as total from Score
group by s_id 
having total>=2;
#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(s_id)=(select count(c_id) 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 Student.*,TIMESTAMPDIFF(YEAR,Student.s_birth,CURDATE()) as age
from Student;
# 47、查询本周过生日的学生
select * from 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 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 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 Student 
where MONTH(DATE_FORMAT(NOW(),'%Y%m%d'))+1 =MONTH(s_birth);