数据库之十四：习题练习

是网上早的题目，答案大部分是我自己写的，部分是别人的答案

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 Course values('01' , '语文' , '02');
insert into Course values('02' , '数学' , '01');
insert into Course values('03' , '英语' , '03');
insert into Teacher values('01' , '张三');
insert into Teacher values('02' , '李四');
insert into Teacher values('03' , '王五');
insert into SC values('01' , '01' , 80);
insert into SC values('01' , '02' , 90);
insert into SC values('01' , '03' , 99);
insert into SC values('02' , '01' , 70);
insert into SC values('02' , '02' , 60);
insert into SC values('02' , '03' , 80);
insert into SC values('03' , '01' , 80);
insert into SC values('03' , '02' , 80);
insert into SC values('03' , '03' , 80);
insert into SC values('04' , '01' , 50);
insert into SC values('04' , '02' , 30);
insert into SC values('04' , '03' , 20);
insert into SC values('05' , '01' , 76);
insert into SC values('05' , '02' , 87);
insert into SC values('06' , '01' , 31);
insert into SC values('06' , '03' , 34);
insert into SC values('07' , '02' , 89);
insert into SC values('07' , '03' , 98);

1.学生表
Student(SID,Sname,Sage,Ssex) --SID 学生编号,Sname 学生姓名,Sage 出生年月,Ssex 学生性别
2.课程表
Course(CID,Cname,TID) --CID --课程编号,Cname 课程名称,TID 教师编号
3.教师表
Teacher(TID,Tname) --TID 教师编号,Tname 教师姓名
4.成绩表
SC(SID,CID,score) --SID 学生编号,CID 课程编号,score 分数

1、查询下月过生日的学生

select sid,sname,sage,ssex from Student
where substr(to_char(sysdate,'yyyy-mm-dd'),6,2)=substr(sage,6,2)

查询下周过生日的学生

select sid,sage,to_char(to_date(sage,'yyyy-mm-dd'),'ww') from student
where to_char(to_date(sage,'yyyy-mm-dd'),'ww')= to_char(sysdate,'ww')+1

查询本周过生日的学生

select sid,sage,to_char(to_date(sage,'yyyy-mm-dd'),'ww') from student
where to_char(to_date(sage,'yyyy-mm-dd'),'ww')= to_char(sysdate,'ww')

查询各学生的年龄

select sname,substr(to_char(sysdate,'yyyy-mm-dd'),1,4) -substr(sage,1,4) from student

查询选修了全部课程的学生信息
（某学生不存在一门课没有选修）

select a.* from student a,sc b
where a.sid=b.sid
group by a.sid,a.sname,a.sage,a.ssex
having count(*)=(select count(*) from course)

检索至少选修两门课程的学生学号

select sid from sc 
group by sid
having count(*)>=2

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 cid,count(*)
from sc 
group by cid
having count(*)>5
order by count(*) desc,cid asc

查询每门功成绩最好的前两名

select * from (select sid,cid,rank() over(partition by cid order by score desc) r from sc 
)where r<3

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 a.* from sc a, sc b
where a.sid=b.sid
and a.cid<>b.cid
and a.score=b.score

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.score from student a,sc b,course c,teacher d
where a.sid=b.sid
and b.cid=c.cid
and c.tid=d.tid
and d.tname='张三'
and score=(select max(e.score) from sc e where e.cid=b.cid)

求每门课程的学生人数

select b.cname,count(*) from sc a,course b
where a.cid=b.cid
group by b.cname

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.sid,a.sname
from student a,sc b
where a.sid=b.sid 
and b.cid='01' 
and b.score>80

查询不及格的课程

select a.sname,c.cname,b.score from student a,sc b,course c
where a.sid=b.sid 
and b.cid = c.cid
and b.score<60

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.sname,c.cname,b.score from student a,sc b,course c
where a.sid=b.sid 
and b.cid = c.cid
and b.score>70

查询所有学生的课程及分数情况

select a.sname,c.cname,b.score from student a,sc b,course c
where a.sid=b.sid
and b.cid=c.cid

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.sname,b.score from student a,sc b,course c
where a.sid=b.sid
and b.cid=c.cid
and c.cname='数学'
and b.score<60

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.SID,A.SNAME,ROUND(AVG(SCORE),2) R FROM STUDENT A,SC B
WHERE A.SID=B.SID
GROUP BY A.SID,A.SNAME
HAVING AVG(SCORE)>=85
ORDER BY R DESC

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 cid,round(avg(score),2) R from sc
group by cid
ORDER BY R DESC,CID ASC

查询1990年出生的学生名单(注：Student表中Sage列的类型是datetime)

select * from student 
where substr(sage,1,4)='1990'

查询同名同性学生名单，并统计同名人数

select sname,ssex,count(*) from Student
group by sname,ssex
having count(*)>1

查询名字中含有"风"字的学生信息

select * from student 
where sname like '%风%'

查询男生、女生人数

select sum(case when ssex='男' then 1 else 0 end),sum(case when ssex='女' then 1 else 0 end)
from Student

查询出只有两门课程的全部学生的学号和姓名

select a.sid,a.sname from student a,sc b
where a.sid=b.sid
group by a.sid,a.sname
having count(*)=2

查询每门课程被选修的学生数

select cid,count(*) from sc 
group by cid

查询各科成绩前三名的记录

select * from (
select cid,score,
rank() 
over(partition by cid order by score desc) r 
from sc)
where r<4

查询学生平均成绩及其名次

select sid,round(avg(score),2),dense_rank() over( order by round(avg(score),2) desc)from SC
group by sid

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 to_char(,'FM9999999999999999.00') as amount

SELECT a.cid,b.cname,
sum(case when a.score>=85 and a.score<100 then 1 else 0 end ) as "100-85",to_char(sum(case when a.score>=85 and a.score<100 then 1 else 0 end )/count(*),'FM9999999999999999.00'),
sum(case when a.score>=70 and a.score<85 then 1 else 0 end ) as "85-70",to_char(sum(case when a.score>=70 and a.score<85 then 1 else 0 end )/count(*),'FM9999999999999999.00'),
sum(case when a.score>=60 and a.score<70 then 1 else 0 end ) as "70-60",to_char(sum(case when a.score>=60 and a.score<70 then 1 else 0 end )/count(*),'FM9999999999999999.00'),
sum(case when a.score>=0 and a.score<60 then 1 else 0 end ) as "0-60",to_char(sum(case when a.score>=0 and a.score<60 then 1 else 0 end )/count(*),'FM9999999999999999.00') from sc a,course b
where a.cid=b.cid
group by a.cid,b.cname

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 a.*,b.cid,b.score 
from student a,(select cid,sid,score,dense_rank() over(partition by cid order by score DESC) R
from SC) b
where a.sid=b.sid
and R>=2 
AND R<=3

查询不同老师所教不同课程平均分从高到低显示

select tname,a.cid,avg(score) avge
from teacher c,course a,sc b
where a.cid=b.cid
and c.tid=a.tid
group by tname,a.cid
order by avge desc

查询学生的总成绩并进行排名

select sid,sum(score) as r from sc 
group by sid 
order by r desc

按各科成绩进行排序，并显示排名

select cid,sid,score,
dense_rank() over(partition by cid order by score) 
from sc
order by cid,score

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.cid,A.cname,max(b.score),min(b.score),avg(b.score),
sum(case when b.score>=60 then 1 else 0 end )/count(*) ,
sum(case when b.score>=70 and b.score<80 then 1 else 0 end)/count(*),
sum(case when b.score>=80 and b.score<90 then 1 else 0 end)/count(*),
sum(case when b.score>=90 then 1 else 0 end)/count(*)
from course a,sc b 
where a.cid=b.cid
GROUP BY a.cid,a.cname;

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.SID 学生编号 , a.Sname 学生姓名 ,
       max(case c.Cname when '语文' then b.score else null end)  语文 ,
       max(case c.Cname when '数学' then b.score else null end)  数学 ,
       max(case c.Cname when '英语' then b.score else null end)  英语 ,
       cast(avg(b.score) as decimal(18,2)) 平均分
from Student a
left join SC b on a.SID = b.SID
left join Course c on b.CID = c.CID
group by a.SID , a.Sname
order by 平均分 desc

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.score from student a,sc b
where b.cid='01'
and score<60
order by score desc

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.sid,a.sname,avg(b.score) from student a,sc b
where exists 
(select c.sid,count(*) from sc c where a.sid=c.sic 
group by c.sid) 
group by a.sid,a.sname

查询没学过"张三"老师讲授的任一门课程的学生姓名

select a.sname from student a,sc b
where not exists (select c.*,d.* from course c ,teacher d 
where cname='张三' and c.cid=b.cid)

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
(有个同学，没有一门课01同学学了，而该同学没学，并且也没学01没学的课程)

select a.* from student a,sc b
where sid<>'01'
group by a.sid
having count(a.sid)=(select count(*) from sc where sid='01')

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
（没有一门课与学号01同学所学相同的同学信息）

select distinct a.* from student a,sc b 
where a.sid=b.sid
and a.sid<>'01' 
and exists (
select * from SC c 
where c.sid='01' 
and b.cid=c.cid )

查询没有学全所有课程的同学的信息

select sid,count(cid) from sc
group by sid
having count(cid)<(select count(cid) from course)

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 distinct a.* from student a,sc b,sc c
where a.sid=b.sid
and b.cid='01'
and not exists (select * from sc c where a.sid=c.sid and c.cid='02')

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 distinct a.* from student a,sc b,sc c
where a.sid=b.sid
and a.sid=c.sid
and b.cid='01'
and c.cid='02'

***查询没学过"张三"老师授课的同学的信息***可以尝试使用exist去写

select e.*
from student e
where e.sid not in (select distinct a.sid
from student a,sc b,course c,teacher d
where a.sid=b.sid
and b.cid=c.cid
and c.tid=d.tid
and tname='张三' )

查询学过"张三"老师授课的同学的信息

select distinct a.sid,a.sname,a.sage,a.ssex
from student a,sc b,course c,teacher d
where a.sid=b.sid
and b.cid=c.cid
and c.tid=d.tid
and tname='张三'

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.sid,a.sname,a.sage,a.ssex,b.score "01分数",c.score "02分数"
from student a,sc b,sc c
where b.cid='01'
and c.cid='02'
and a.sid=b.sid
and a.sid=c.sid
and b.score>c.score

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.sid,a.sname,avg(b.score) "平均成绩"
from student a,sc b
where a.sid=b.sid
group by a.sid,a.sname
having avg(b.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.sid,a.sname,sount(a.sid),sum(b.score)
from student a,sc b
where a.sid=b.sid
group by sid,sname

查询"李"姓老师的数量

select count(*) from Teacher
where Tname like '李%'

来源：https://www.cnblogs.com/chenbao1012/p/11846680.html

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select

cname