一.建表和載入資料
1.student表
create table if not exists student(s_id int,s_name string,s_birth string,s_sex string)
row format delimited
fields terminated by ','
;
load data local inpath '/root/data.txt' into table student;

2.course表
create table if not exists course(c_id int,c_course string,t_id int)
row format delimited
fields terminated 
 
by ','
;
load data local inpath '/root/data.txt' into table course;

3.teacher表
create table if not exists teacher(t_id int,t_name string)
row format delimited
fields terminated by ','
;
load data local inpath '/root/data.txt' into table teacher;
4.score表
create table if not exists score(s_id int,c_id int
 
, s_score DOUBLE)
row format delimited
fields terminated by ','
;
load data local inpath '/root/data.txt' into table score;

二.查詢"01"課程比"02"課程成績高的學生的資訊及課程分數?
答案①：
select stu.*,c.*
from student stu
join score a on a.c_id = '01' and a.s_id= stu.s_id
left join score b on b.c_id = '02' and b.s_id= stu.s_id
join
 
 score c on c.s_id= stu.s_id
where a.s_score > b.s_score or b.s_score is null
;
答案②：
select stu.*,c.*
from student stu
left join score a on a.c_id = '02' and a.s_id= stu.s_id
join score b on b.c_id = '01' and b.s_id= stu.s_id
join score c on c.s_id= stu.s_id
where a.s_score < b.s_score or a.s_score is null
;
三.查詢"01"課程比"02"課程成績低的學生的資訊及課程分數:
答案①：
select stu.*,c.*
from student stu
join score a on a.c_id = '02' and a.s_id= stu.s_id
left join score b on b.c_id = '01' and b.s_id= stu.s_id
join score c on c.s_id= stu.s_id
where a.s_score > b.s_score or b.s_score is null
;
答案②：
select stu.*,c.*
from student stu
left join score a on a.c_id = '01' and a.s_id= stu.s_id
join score b on b.c_id = '02' and b.s_id= stu.s_id
join score c on c.s_id= stu.s_id
where a.s_score < b.s_score or a.s_score is null
;
總結：對於二題和三題的查詢連線的方法：誰大就把誰放在左邊,誰小就把誰捨棄。
四.查詢平均成績大於等於60分的同學的學生編號和學生姓名和平均成績？
答案①：
select 
a.s_id,stu.s_name,avg(a.s_score) as avgscore
from score a
join student stu on a.s_id = stu.s_id
group by a.s_id,stu.s_name
having avgscore >= 60
;
答案②：
select 
a.s_id,stu.s_name,avg(a.s_score)>=60
from score a
join student stu on a.s_id = stu.s_id
group by a.s_id,stu.s_name
;
五.查詢平均成績小於60分的同學的學生編號和學生姓名和平均成績?
答案①：
select 
a.s_id,stu.s_name,avg(a.s_score) as avgscore
from score a
join student stu on a.s_id = stu.s_id
group by a.s_id,stu.s_name
having avgscore < 60
union all
select stu.s_id,stu.s_name,NULL as avgscore
from student stu
left join score a on stu.s_id = a.s_id
where a.s_score is null
;
六.查詢所有同學的學生編號、學生姓名、選課總數、所有課程的總成績
答案：
select stu.s_id,stu.s_name,count(sc.s_id) as totalSubjects,sum(sc.s_score) as sumScores     
from student stu left join score sc on stu.s_id=sc.s_id
group by stu.s_id,stu.s_name;
七.查詢"李"姓老師的數量？
select count(1)from teacher where t_name like '李%';
八.查詢學過"張三"老師授課的同學的資訊?
select distinct stu.*
from student stu 
join score sc on stu.s_id=sc.s_id
join course co on sc.c_id=co.c_id
join teacher te on co.t_id =te.t_id
where te.t_name='張三';
九.查詢沒學過"張三"老師授課的同學的資訊?
select *
from student stu
join teacher te on te.t_name='張三'
join course co on te.t_id=co.t_id
left join score sc on stu.s_id=sc.s_id and co.c_id=sc.c_id
where sc.s_score is null;
十.查詢學過編號為"01"並且也學過編號為"02"的課程的同學的資訊?
select stu.*,sc.*
from student stu,score sc,score sc1
where stu.s_id=sc.s_id and stu.s_id=sc1.s_id
and sc.c_id=1 and sc1.c_id=2;
十一.查詢學過編號為"01"但是沒有學過編號為"02"的課程的同學的資訊:
select stu.*
from student stu
join score sc on sc.s_id =stu.s_id and sc.c_id = '01' 
where not exists (select 1 from score sc1 where sc1.c_id = '02' and stu.s_id = sc1.s_id)
;
十二.查詢沒有學全所有課程的同學的資訊?
select distinct stu.*
from student stu
join score sc
left join course co
on stu.s_id=sc.s_id and sc.c_id=co.c_id
where sc.s_score is null;
十三.查詢至少有一門課與學號為"01"的同學所學相同的同學的資訊?
select distinct stu.*
from student stu
join score sc on stu.s_id=sc.s_id
where stu.s_id <> 1 and sc.c_id in
(select c_id from score where s_id=1);

十四.查詢和"01"號的同學學習的課程完全相同的其他同學的資訊?
select 

十五.查詢沒學過"張三"老師講授的任一門課程的學生姓名?
select stu.*
from student stu
join teacher te on te.t_name = '張三'
join course co on co.t_id = te.t_id
left join score sc on sc.c_id = co.c_id and sc.s_id = stu.s_id
where sc.s_score is null;
十六.查詢兩門及其以上不及格課程的同學的學號，姓名及其平均成績?
select 
*
from student stu 
join score sc on sc.s_id = stu.s_id
where sc.s_score < 60
;

十七.檢索"01"課程分數小於60，按分數降序排列的學生資訊?
select *
from student stu
join score sc on sc.s_id = stu.s_id
where sc.c_id = 1 and sc.s_score < 60
order by sc.s_score desc;
十八.按平均成績從高到低顯示所有學生的所有課程的成績以及平均成績？
select *,
round(avg(sc.s_score) over(distribute by sc.s_id),2) as avg1
from score sc
order by avg1 desc,sc.s_score desc;
總結：在這裡啊，round是hive的內建函式，其功能是四捨五入。
十九..查詢各科成績最高分、最低分和平均分：以如下形式顯示：課程ID，課程name，最高分，最低分，平均分，及格率，中等率，優良率，優秀率:
-- 及格為>=60，中等為：70-80，優良為：80-90，優秀為：>=90?
select 
co.c_id,
co.c_course,
max(sc.s_score),
min(sc.s_score),
round(avg(sc.s_score),3),
round(sum(case when sc.s_score >=60 then 1 else 0 end)/count(1) *100,3) as `及格率`,
round(sum(case when sc.s_score between 70 and 79 then 1 else 0 end)/count(1) *100,3) as `中等率`,
round(sum(case when sc.s_score between 80 and 89 then 1 else 0 end)/count(1) *100,3) as `優良率`,
round(sum(case when sc.s_score>=90 then 1 else 0 end)/count(1) *100,3) as `優秀率`
from score sc
join course co on sc.c_id=co.c_id
group by co.c_id,co.c_course;

二十.按各科成績進行排序，並顯示排名:– row_number() over()分組排序功能?
select *,
row_number() over(distribute by c_id sort by s_score desc) from score;
二十一.查詢學生的總成績並進行排名？
select s_id,sum(s_score) as sumScores
from score
group by s_id
order by sumScores desc;
二十二:查詢不同老師所教不同課程平均分從高到低顯示?
select t_id,sc.c_id,round(avg(sc.s_score),2) as avgscore
from score sc
join course co on sc.c_id=co.c_id
group by t_id,sc.c_id
order by t_id,avgscore desc;
二十三.查詢所有課程的成績第2名到第3名的學生資訊及該課程成績?
select *
from ( select *,
row_number() over(distribute by c_id sort by s_score desc) as rm
from score ) a
where a.rm between 2 and 3;
二十四.統計各科成績各分數段人數：課程編號,課程名稱,[100-85],[85-70],[70-60],[0-60]及所佔百分比?
select c_id,
sum(case when s_score>=85 then 1 else 0 end) as 85score,
sum(case when s_score between 70 and 84 then 1 else 0 end) as 70score,
sum(case when s_score between 60 and 69 then 1 else 0 end) as 60score,
sum(case when s_score<60 then 1 else 0 end) as 0score,
count(1) as totalscore
from score group by c_id;
二十五.查詢學生平均成績及其名次?
select *,
row_number() over(sort by a.avgscore desc) as rm
from (
select s_id,round(avg(s_score),2) as avgscore
from score group by s_id) a;
二十六.查詢各科成績前三名的記錄三個語句?
select *
from (
select *,
row_number() over(distribute by c_id sort by s_score desc) as rm,
rank() over(distribute by c_id sort by s_score desc) as rk,
dense_rank() over(distribute by c_id sort by s_score desc) as drk
from score) a where a.rm<4;
二十七.查詢每門課程被選修的學生數?
select c_id,count(1) as `學生人數`
from score
group by c_id;
二十八.查詢出只有兩門課程的全部學生的學號和姓名？
select stu.s_id,stu.s_name
from student stu
join score sc on sc.s_id=stu.s_id
group by stu.s_id,stu.s_name
having count(1)=2;
二十九.查詢男生、女生人數?
select s_sex,count(1) as totalstu
from student 
group by s_sex;
三十.查詢名字中含有"風"字的學生資訊?
select *
from student
where s_name like '%風%' ;
三十一.查詢同名同性學生名單，並統計同名人數?
select s_name,s_sex,count(1) as totalstu
from student
group by s_name,s_sex
having totalstu>1;
三十二.查詢1990年出生的學生名單?
select *
from student
where s_birth like '1990%';
select *
from student
where substr(s_birth,0,4)='1990';
三十三.查詢每門課程的平均成績，結果按平均成績降序排列，平均成績相同時，按課程編號升序排列?
select c_id,round(avg(s_score),2) as avgscore
from score
group by c_id
order by avgscore desc,c_id asc;
三十四:查詢平均成績大於等於85的所有學生的學號、姓名和平均成績?
select stu.s_name,avg(sc.s_score) as avgscore
from student stu 
join score sc on stu.s_id=sc.s_id
group by stu.s_id,stu.s_name
having avgscore>85;
三十五:查詢課程名稱為"數學"，且分數低於60的學生姓名和分數?
select stu.s_name,sc.s_score
from student stu
join score sc on stu.s_id=sc.s_id
join course co on sc.c_id=co.c_id and co.c_course='數學'
where sc.s_score<60;
三十六：查詢所有學生的課程及分數情況？
select *
from student stu
join score sc on stu.s_id=sc.s_id
right join course co on sc.c_id=co.c_id
;
三十七:查詢任何一門課程成績在70分以上的學生姓名、課程名稱和分數?
select stu.s_name,co.c_course,sc.s_score
from student stu
join score sc on stu.s_id=sc.s_id
join course co on sc.c_id=co.c_id
group by stu.s_id,stu.s_name,co.c_course,sc.s_score  having min(sc.s_score)>=70;
三十八:查詢課程不及格的學生?
select stu.*
from student stu
join score sc on stu.s_id=sc.s_id
where sc.s_score<60;
三十九:查詢課程編號為01且課程成績在80分以上的學生的學號和姓名？
select stu.s_id,stu.s_name,sc.c_id,sc.s_score
from student stu
join score sc on stu.s_id=sc.s_id
where c_id=1 and s_score>=80;
四十:每門課程的學生人數?
select sc.c_id,co.c_course,count(1) as stunum
from score sc
join course co on sc.c_id=co.c_id
group by sc.c_id,co.c_course;
四十一:查詢選修"張三"老師所授課程的學生中，成績最高的學生資訊及其成績?
select *
from (
select
dense_rank() over(distribute by sc.c_id sort by sc.s_score desc) drk
from score sc
join course co on sc.c_id=co.c_id
join teacher te on co.t_id=te.t_id
where te.t_name='張三') aa
where aa.drk=1;
四十二:查詢不同課程成績相同的學生的學生編號、課程編號、學生成績?
①select distinct sc.s_id,sc.c_id,sc.s_score
from score sc,score sc1
where sc.c_id<>sc1.c_id and sc.s_score=sc1.s_score and sc.s_id=sc1.s_id;
②select distinct sc.s_id,sc.c_id,sc.s_score
from score sc,score sc1
where sc.c_id !=sc1.c_id and sc.s_score=sc1.s_score and sc.s_id=sc1.s_id;
四十三:查詢每門課程成績最好的前三名?
select *
from (select *,
row_number() over(distribute by c_id sort by s_score desc) rn
from score) aa
where aa.rn<=3;
四十四：統計每門課程的學生選修人數（超過5人的課程才統計）？
select c_id,count(*) as stunum
from score
group by c_id
having stunum>5
order by c_id asc,stunum desc;
四十五：檢索至少選修兩門課程的學生學號？
select s_id,count(1) as coursenum
from score
group by s_id having coursenum >=2;
四十六：查詢選修了全部課程的學生資訊？
select stu.s_id,stu.s_name
from student stu
join score sc on stu.s_id=sc.s_id
left join course co on sc.c_id=co.c_id
group by stu.s_id,stu.s_name
having sum(case when sc.s_score is null then 1 else 0 end)=0;
四十七：查詢各學生的年齡(週歲)？
select 
s_birth,
year(current_date())-year(s_birth)-
(case 
when month(current_date())>month(s_birth)
then 0
when month(current_date())=month(s_birth)
and
day(current_date())>=day(s_birth)
then 0 else 1 end)
from student;
四十八:查詢本週過生日的學生?
select *
from student
where weekofyear(s_birth)=weekofyear(current_date());
四十九：查詢下週過生日的學生？
select *
from student
where weekofyear(s_birth)=weekofyear(current_date())+1;
四十九：查詢上週過生日的學生？
select *
from student
where weekofyear(s_birth)=weekofyear(current_date())-1;
五十:查詢本月過生日的學生?
select *
from student
where month(s_birth)=month(current_date());
五十:查詢上月過生日的學生?
select *
from student 
where month(s_birth)=month(current_date())-1;
五十:查詢下月過生日的學生?
select *
from student 
where month(s_birth)=month(current_date())+1;
五十一：查詢12月份過生日的學生？
①select *
from student
where month(s_birth)=12;

②select *
from student 
where substring(s_birth,4,2)=12;