SQL練習

學生表：STUDENT(S#,SNAME,SAGE,SSEX)

教師表：TEACHER(T#,TNAME)

課程表：COURSE(C#,CNAME,T#)

成績表：SC(S#,C#,SCORE)

--一、查詢課程編號爲「001」的課程比「002」的課程成績高的全部學生的學號
select A.s#
from (select * from A_sc where c# = '001') A
inner join (select * from A_sc where c# = '002') B on A.s# = B.s#
where A.score > B.score;

--三、查詢全部學生的學號、姓名、選課數、總成績
select A.s#, A.sname, nvl(B.c, 0), nvl(B.s, 0)
from A_student A 
left join (select s#, count(*) c, sum(score) s from A_sc group by s#) B on A.s# = B.s#;

SELECT A_STUDENT.S#, A_STUDENT.SNAME, COUNT(A_SC.C#), nvl(SUM(SCORE),0)
FROM A_STUDENT
LEFT OUTER JOIN A_SC ON A_STUDENT.S#=A_SC.S#
GROUP BY A_STUDENT.S#, SNAME;

--五、查詢沒學過「李美玲」老師課的學生的學號、姓名
select s#,sname
from A_student D 
where s# not in
(select s# from A_SC A inner join A_course B on A.c# = B.c# inner join A_teacher C on B.t# = C.t# where C.tname = '李美玲');

--六、查詢學過編號爲「001」的課程而且也學過編號爲「002」的課程的學生的學號、姓名
select A.s#, A.sname
from A_student A
inner join (select s# from A_sc where c# = '001') B on A.s# = B.s#
inner join (select s# from A_sc where c# = '002') C on A.s# = C.s#;

--七、查詢學過「李美玲」老師所教的全部課的學生的學號、姓名,
select C.s#, D.sname from (
  select s#, c# from A_sc 
  where c# in (select c# from A_course A inner join A_teacher B on A.t# = B.t# where B.tname = '李美玲')) C
inner join A_student D on C.s# = D.s#
group by C.s#, D.sname
having count(*) = (select count(*) from A_course A inner join A_teacher B on A.t# = B.t# where B.tname = '李美玲');

--要求 老師名字惟一

--九、查詢全部課程成績小於90分的學生的學號、姓名
select A.s#, A.sname
from A_student A 
inner join (select s#, count(*) c from A_sc group by s#) B on A.s# = B.s#
inner join (select s#, count(*) c from A_sc where score < 90 group by s#) C on A.s# = C.s#
where B.c = C.c;

select s#,sname from A_student 
where s# not in 
(select s# from A_sc where score >= 90);

--十、查詢沒有學全全部課的學生的學號、姓名
select s#,sname from A_student where s# not in
(select s# from A_sc group by s# having count(*) = (select count(*) from A_course));

select A.s#, A.sname from A_student A
inner join A_sc B on A.s# = B.s#
group by A.s#,A.sname
having count(B.c#) < (select count(*) from A_course);

--十一、查詢至少有一門課與學號爲「2018001」的學生所學課程相同的學生的學號和姓名
select distinct A.s#,sname
from A_student A
inner join A_sc B on A.s# = B.s# where c# in 
(select c# from A_sc where s# = '2018001');

--十二、查詢所學課程和學號爲「2018002」的學生全部課程同樣的其餘學生的學號和姓名
select A.s#,sname
from A_student A
inner join A_sc B on A.s# = B.s# 
where c# in (select c# from A_sc where s# = '2018002')
group by A.s#,sname 
having count(*) = (select count(*) from A_sc where s# = '2018002');

結果：2018002李四學的課程，張三都學了，且張三有其餘課程，李四沒有學，取的子集，且包含自己。

--1八、查詢各科成績最高和最低的分
select c#,max(score),min(score)
from A_sc 
group by c#
order by c#;

--1九、按各科平均成績從低到高和及格率的百分數從高到低排列，以以下形式顯示：課程號|課程名|平均成績|及格百分數
select A.c#, cname, round(avg(score), 2), round(sum(case when score >= 60 then 1 else 0 end)/count(*) * 100)||'%'
from A_course A
inner join A_sc B on A.c# = B.c#
group by A.c#,cname
order by avg(score), 
sum(case when score >= 60 then 1 else 0 end)/count(*) desc;

--20、查詢以下課程平均成績和及格率的百分數（用1行顯示），其中企業管理爲001，馬克思爲002，UML爲003，數據庫爲004
select
round(sum(case c# when '001' then score else 0 end)/sum(case c# when '001' then 1 else 0 end), 2) 企業管理平均分, 
round(sum(case when c#='001' and score>60 then 1 else 0 end)/sum(case c# when '001' then 1 else 0 end)*100, 2)||'%' 企業管理及格率,
sum(case c# when '002' then score else 0 end)/sum(case c# when '002' then 1 else 0 end) 馬克思平均分,
sum(case c# when '004' then score else 0 end)/sum(case c# when '004' then 1 else 0 end) 數據庫平均分
from A_sc;

--2一、查詢不一樣老師所教不一樣課程平均分從高到低顯示
select B.c#,B.cname,round(avg(score)),C.t#,C.tname
from A_sc A
inner join A_course B on A.c# = B.c#
inner join A_teacher C on B.t# = C.t#
group by B.c#,B.cname,C.t#,C.tname
order by avg(score) desc;