測試表格

--1.學生表
Student(S#,Sname,Sage,Ssex) 

--S# 學生編號,Sname 學生姓名,Sage 出生年月,Ssex 學生性別

--2.課程表 
Course(C#,Cname,T#) 

--C# --課程編號,Cname 課程名稱,T# 教師編號

--3.教師表 
Teacher(T#,Tname)

 --T# 教師編號,Tname 教師姓名

--4.成績表 
SC(S#,C#,score)

 --S# 學生編號,C# 課程編號,score 分數

建立測試資料

學生表 Student

create table Student(S# varchar(10),Sname nvarchar(10),Sage datetime,Ssex nvarchar(10))
insert into Student values('01' , N'趙雷' , '1990-01-01' , N'男')
insert into Student values('02' , N'錢電' , '1990-12-21' , N'男')
insert into Student values('03' , N'孫風' , '1990-05-20' , N'男')
insert into Student values('04' , N'李雲' , '1990-08-06' , N'男')
insert into Student values('05' , N'周梅' , '1991-12-01' , N'女')
insert into Student values('06' , N'吳蘭' , '1992-03-01' , N'女')
insert into Student values('07' , N'鄭竹' , '1989-07-01' , N'女')
insert into Student values('08' , N'王菊' , '1990-01-20' , N'女')

科目表 Course
create table Course(C# varchar(10),Cname nvarchar(10),T# varchar(10))
insert into Course values('01' , N'語文' , '02')
insert into Course values('02' , N'數學' , '01')
insert into Course values('03' , N'英語' , '03')

教師表 Teacher
create table Teacher(T# varchar(10),Tname nvarchar(10))
insert into Teacher values('01' , N'張三')
insert into Teacher values('02' , N'李四')
insert into Teacher values('03' , N'王五')

成績表 SC
create table SC(S# varchar(10),C# varchar(10),score decimal(18,1))
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、查詢“001”課程比“002”課程成績高的所有學生的學號
select a.S# from (select S#,score from SC where C#='001')a, 
(select s#,score from SC where c#='002')b Where a.score>b.score and a.s# = b.s#;
2、查詢平均成績大於60分的同學的學號和平均成績
select S#, avg(score) from sc group by S# having avg(score)>60
3、查詢所有同學的學號、姓名、選課數、總成績
select student.S_id, student.Sname, count(sc.C_id), sum(score) from student 
left join SC on student.S_id = SC.S_id group by Student.S_id, Sname
4、查詢姓‘李’的老師的個數：
select count(distinct(Tname)) 
from teacher 
where tname like '李%';
5、查詢沒有學過“葉平”老師可的同學的學號、姓名：
select student.S#, student.Sname 
from Student 
where S# not in (select distinct(SC.S#) from SC,Course,Teacher 
where sc.c#=course.c# AND teacher.T#=course.T# AND Teahcer.Tname ='葉平');
6、查詢學過“葉平”老師所教的所有課的同學的學號、姓名：
select S#,Sname   from Student    
where S# in (select S# from SC ,Course ,Teacher 
where SC.C#=Course.C# and Teacher.T#=Course.T# 
and Teacher.Tname='葉平' group by S# 
having count(SC.C#)=(select count(C#) from Course,Teacher  
where Teacher.T#=Course.T# and Tname='葉平'));
7、查詢學過“011”並且也學過編號“002”課程的同學的學號、姓名：
select Student.S#,Student.Sname 
from Student,SC where Student.S#=SC.S# 
and SC.C#='001'and 
exists( Select * from SC as SC_2 where SC_2.S#=SC.S# and SC_2.C#='002');
8、查詢課程編號“002”的成績比課程編號“001”課程低的所有同學的學號、姓名：
Select S#,Sname 
from (select Student.S#,Student.Sname,score ,
(select score from SC SC_2 where SC_2.S#=Student.S# and SC_2.C#='002') score2    
from Student,SC 
where Student.S#=SC.S# and C#='001') S_2 
where score2 < score; 
9、查詢所有課程成績小於60的同學的學號、姓名：
select S#, sname 
from student 
where s# not in 
(select student.s# from student, sc where s.s# = sc.s# and score>60);
10、查詢沒有學全所有課的同學的學號、姓名：
select student.s#, student.sname 
from student, sc
where student.s#=sc.s# 
group by student.s#, student.sname 
having count(c#)<(select count(c#) from course);
11、查詢至少有一門課與學號為“1001”同學所學相同的同學的學號和姓名：
select s#, Sname 
from Student, SC 
where student.s# = sc.s# 
and c# in (select c# from SC where s#='1001');
12、查詢至少學過學號為“001”同學所有一門課的其他同學學號和姓名；
select distinct sc.s# , sname 
from student, sc 
where student.s#=sc.s# 
and c# in (select C# from sc where s#='001');
13、把“SC”表中“葉平”老師教的課的成績都更改為此課程的平均成績：
Update Sc Set Score=(Select Avg(s2_Score) From sc s2 Where s2.c#=sc.c#)  
Where c# IN
(Select c# From sc cs INNER JOIN Teacher tc ON cs.t#=tc.t# WHERE tname ='葉平')
14、查詢和“1002”號的同學學習的課程完全相同的其他同學學號和姓名：
select s# from sc where c#  in 
(select c# from sc where s#='1002') 
group by s# having count(*)=
(select count(*) from sc where s#='1002');
 這個寫法是有問題的，如果“1002”同學的學習課程是其它同學的子集，那麼也會篩選出來；
正確寫法如下：子集且記錄數相同
select t1.s_id from 
(select s_id,count(distinct c_id) as cnt1 from sc where c_id in
(select c_id from sc where s_id=2) and s_id <> 2 group by s_id 
having count(distinct c_id)=(select count(distinct c_id) from sc where s_id=2)) t1,
(select s_id,count(distinct c_id) as cnt2 from sc  group by s_id) t2
where t1.s_id=t2.s_id and t1.cnt1=t2.cnt2 
15、刪除學習“葉平”老師課的SC表記錄：
delect sc 
from course, Teacher 
where course.c#=sc.c# 
and course.t#=teacher.t# 
and tname='葉平';
16、向SC表中插入一些記錄，這些記錄要求符合以下條件：沒有上過編號“003”課程的同學學號、002號課的平均成績：
Insert SC select S#,'002',
(Select avg(score) from SC where C#='002') 
from Student where S# not in (Select S# from SC where C#='002');
17、按平均成績從高到低顯示所有學生的“資料庫”、“企業管理”、“英語”三門的課程成績，按如下形式顯示：學生ID，資料庫，企業管理，英語，有效課程數，有效平均分：
select s_id as 學生ID,
(select score from sc where sc.s_id=t.s_id and c_id=1) as 資料庫,
(select score from sc where sc.s_id=t.s_id and c_id=2) as 企業管理,
(select score from sc where sc.s_id=t.s_id and c_id=3) as 英語,
count(*) as 有效課程數, avg(t.score) as 平均成績,rank() over(order by avg(t.score) desc) as 名次
from sc  t
group by s_id 
order by avg(t.score) asc
此題很經典，沒做出來。rank over() 裡面是是計算名次的排序；order by是記錄展示的排序
18、查詢各科成績最高和最低的分： 以如下的形式顯示：課程ID，最高分，最低分
select L.c# as 課程ID, L.score as 最高分,
R.score as 最低分
from sc L, sc R 
where L.c# = R.c# 
and L.score = (select max(IL.score) 
        from sc IL, student as IM 
        where L.c#=IL.c# and IM.s#=IL.s#
        group by IL.c#)
and R.score = (select min(IR.score)
        from sc as IR
        where R.c#=IR.c#
        group by IR.c#);
select c_id,max(score),min(score) from sc group by c_Id;
19、按各科平均成績從低到高和及格率的百分數從高到低順序：
SELECT t.C# AS 課程號,
max(course.Cname)AS 課程名,
isnull(AVG(score),0) AS 平均成績,
100 * SUM(CASE WHEN  isnull(score,0)>=60 THEN 1 ELSE 0 END)/COUNT(*) AS 及格百分數     
FROM SC T,Course     
where t.C#=course.C#     
GROUP BY t.C#      
ORDER BY 100 * SUM(CASE WHEN  isnull(score,0)>=60 THEN 1 ELSE 0 END)/COUNT(*) DESC 
select c_id 課程編號,round(avg(score),2) 平均分,
round(sum(case when score>59 then 1 else 0 end)/count(1)*100.00,2)||'%' 及格率 from sc
group by c_id order by 平均分 asc,及格率 desc;
20、查詢如下課程平均成績和及格率的百分數(用”1行”顯示): 企業管理（001），馬克思（002），OO&UML （003），資料庫（004）：
21、查詢不同老師所教不同課程平均分從高到低顯示：
 SELECT max(Z.T#) AS 教師ID,
 MAX(Z.Tname) AS 教師姓名,
 C.C# AS 課程ID,
 AVG(Score) AS 平均成績     
 FROM SC AS T,Course AS C ,Teacher AS Z    
 where T.C#=C.C# and C.T#=Z.T#   
 GROUP BY C.C#    
 ORDER BY AVG(Score) DESC
22、查詢如下課程成績第3名到第6名的學生成績單：企業管理(001)，馬克思(002)，UML(003)，資料庫(004)：
23、統計下列各科成績，各分數段人數：課程ID，課程名稱，[100-85],[85-70],[70-60],[ 小於60] ：
SELECT SC.C# as 課程ID, Cname as 課程名稱,
SUM(CASE WHEN score BETWEEN 85 AND 100 THEN 1 ELSE 0 END) AS [100 - 85]  ,
SUM(CASE WHEN score BETWEEN 70 AND 85 THEN 1 ELSE 0 END) AS [85 - 70],
SUM(CASE WHEN score BETWEEN 60 AND 70 THEN 1 ELSE 0 END) AS [70 - 60],
SUM(CASE WHEN score < 60 THEN 1 ELSE 0 END) AS [60 -]     
FROM SC,Course     
where SC.C#=Course.C#     
GROUP BY SC.C#,Cname;
select c_id 課程ID,
       (select cname from course t1 where t1.c_id=t2.c_id) 課程名稱,
       count(distinct case when score between 85 and 100 then s_id end ) "[85-100分]人數",
       count(distinct case when score between 70 and 85 then s_id end ) "[75-85分]人數",
       count(distinct case when score between 60 and 70 then s_id end ) "[60-70]人數",
       count(distinct case when score <60 then s_id end ) "小於60分人數"
       from sc t2 group by c_id ;
注：這種寫法更好一點，可以排除，同人同科目錯誤錄入了兩條記錄的情況；
24、查詢學生平均成績及其名次：
SELECT 1+(SELECT COUNT( distinct 平均成績)                
FROM (SELECT S#,AVG(score) AS 平均成績                       
FROM SC                   
GROUP BY S#  ) AS T1  WHERE 平均成績 > T2.平均成績) as 名次,       
S# as 學生學號,平均成績      
FROM (SELECT S#,AVG(score) 平均成績             
FROM SC         
GROUP BY S# ) AS T2      
ORDER BY 平均成績 desc; 
select s_id 學號,avg(score) 平均成績,rank() over(order by avg(score) desc) 名次 from sc group by s_id;
25、查詢各科成績前三名的記錄（不考慮成績並列情況）：
SELECT t1.S# as 學生ID,t1.C# as 課程ID,Score as 分數       
FROM SC t1        
WHERE score IN 
(SELECT TOP 3 score               
FROM SC               
WHERE t1.C#= C#             
ORDER BY score DESC)   
select s_id,c_id,dense_rank() over(partition by c_id order by score desc) rank from sc;  
注：oracle沒有top N的寫法；  
 
26、查詢每門課程被選修的學生數：
select c#, count(s#) 
from sc 
group by c#;
27、查詢出只選修一門課程的全部學生的學號和姓名：
select t2.s_Id,t2.sname from student t2 where t2.s_id 
in(select s_Id from sc group by sc.s_id having count(distinct sc.c_id)=1);
 
select t1.s_id,t2.sname from sc t1,student t2 where t1.s_id=t2.s_id 
group by t1.s_id,t2.sname having count(distinct t1.c_id)=1
 注：寫法2 可加深對group by的理解，實際根據t1.s_id已經能夠唯一定位，加上t2.sname完全是語法需要
28、查詢男生、女生人數：
select count(Ssex) as 男生人數 
from student 
group by Ssex 
having Ssex='男'；
select count(Ssex) as 女生人數 
from student 
group by Ssex 
having Ssex='女';
select (case when ssex='M' then '男' else '女' end) 性別,count(1) 人數 from student group by ssex;
注：注意單引號，資料庫裡只識別單引號。
29、查詢姓“張”的學生名單：
select sname 
from student 
where sname like '張%';
30、查詢同名同姓的學生名單，並統計同名人數：
select sanme,count(*) 
from student 
group by sname 
havang count(*)>1;
31、1981年出生的學生名單（注：student表中sage列的型別是datetime）:
select sname, convert(char(11),DATEPART(year,sage)) as age
from student 
where convert(char(11),DATEPART(year,Sage))='1981';
32、查詢平均成績大於85的所有學生的學號、姓名和平均成績：
select Sname,SC.S# ,avg(score)     
from Student,SC      
where Student.S#=SC.S# 
group by SC.S#,Sname 
having    avg(score)>85;
33、查詢每門課程的平均成績，結果按平均成績升序排序，平均成績相同時，按課程號降序排列：
select C#, avg(score) 
from sc 
group by c# 
order by avg(score), c# desc;
34、查詢課程名稱為“資料庫”，且分數低於60的學生名字和分數：
select sname, isnull(score,0) 
from student, sc ,course 
where sc.s#=student.s#  and sc.c#=course.c# and course.cname='資料庫' and score<60;
35、查詢所有學生的選課情況：
select sc.s#,sc.c#,sname,cname 
from sc,student course 
where sc.s#=student.s# and sc.c#=course.c#;
36、查詢任何一門課程成績在70分以上的姓名、課程名稱和分數：
select distinct student.s#,student.sname,sc.c#,sc.score 
from student,sc 
where sc.score>=70 and sc.s#=student.s#;
37、查詢課程和不及格人數，並按課程號從大到小的排列：
select c# 
from sc 
where score<60 
order by c#;
select c_id , count(1) from sc where score < 60 group by c_id order by c_id;
注：很好的考察了對group by 用法的理解
38、查詢課程編號為“003”且課程成績在80分以上的學生的學號和姓名：
select sc.s#,student.sname 
from sc,student 
where sc.s#=student.s# and score>80 and c#='003';
39、求選了課程的學生人數：
select count(*) from sc;
select count(distinct c_id) from sc where score is not null;
注：感覺這樣更嚴謹
40、查詢選修“葉平”老師所授課程的學生中，成績最高的學生姓名及其成績：
select student.sname,score 
from student,sc,course c, teacher 
where student.s#=sc.S# and sc.c#=c.c#
and c.T#=teacher.T#
and teacher.tname='葉平' 
and sc.score=(select max(score) from sc where c#=c.c#);
select t4.sname 姓名,t3.score 成績 from sc t3,student t4 where t3.s_id=t4.s_id and  t3.score=
(select max(score) from sc 
where c_id in(select t1.c_id from course t1,teacher t2 where t1.t_id=t2.t_id and t2.tname='葉平'));
注：連線4張表
41、查詢各個課程及相應的選修人數：
select count(*) from sc group by c#;
42、查詢不同課程成績相同的學生和學號、課程號、學生成績：
select distinct a.s#,b.score 
from sc a ,sc b 
where a.score=b.score 
and a.c#<>b.c#;
select t1.* from 
sc t1,sc t2 where 
t1.score=t2.score and t1.s_id<>t2.s_id and t1.c_id<>t2.c_id order by t1.score;
注：使用自連線的例子
43、查詢每門課程成績最好的前兩名：
select t1.s# as 學生ID,t1.c#  課程ID, Score as 分數
from sc t1 
where score in (select top 2 score from sc 
        where t1.c#=c#
        order by score desc)
order by t1.c#;
select (select cname from course where c_id=t1.c_id) 課程名,t2.sname 學生姓名,t1.rank 排名 from 
(select c_id,s_id,rank() over(partition by c_id order by score desc) rank from sc) t1,student t2 
where t1.s_id=t2.s_id and t1.rank <3 
注：partition by 以前沒用過，注意下用法；
44、統計每門課程的學生選修人數(超過10人的課程才統計)。要求輸出課程號和選修人數，查詢結果按人數降序排序，若人數相同，按課程號升序排序：
select c_id,count(distinct s_id) from sc group by c_id 
having count(distinct s_id)>10 order by count(distinct s_id) desc,c_id asc;
45、檢索至少選修兩門課程的學生學號：
select s# 
from sc 
group by s# 
having count(*)>=2;
46、查詢全部學生選修的課程和課程號和課程名：
select c# ,cname
from course 
where c# in (select c# from sc group by c#);
47、查詢沒學過”葉平”老師講授的任一門課程的學生姓名：
select sname 
from student 
where s# not in (select s# from course,teacher,sc where course.t#=teacher.t# and sc.c#=course.c# 
and tname='葉平');
select distinct  t3.s_id,t3.sname from student t3,sc t4 where t3.s_id=t4.s_id and t4.c_id 
not in(select t1.c_id from course t1,teacher t2 where t1.t_id=t2.t_id and t2.tname='葉平');
注：此題集合的思想，1、學過葉平的課的學生；2、葉平教過的課    取相反數
48、查詢兩門以上不及格課程的同學的學號以及其平均成績：
select s#,avg(isnull(score,0)) 
from sc 
where s# in (select s# from sc where score<60 group by s# having count(*)>2)
group by s#;
select s_id,avg(score) from sc group by s_id 
having count(distinct case when score < 60 then c_id end)>2
49、檢索“004”課程分數小於60，按分數降序排列的同學學號：
select s# 
from sc 
where c#='004' 
and score<60 
order by score desc;
50、刪除“002”同學的“001”課程的成績：
delect from sc 
where s#='002' 
and c#='001';