有下列四個表：

Student(SID, Sname, Sage, Ssex) 學生表

Course(CID, Cname, TID) 課程表

SC(SID, CID, score) 成績表

Teacher(TID, Tname) 教師表

問題：

1、查詢“001”課程比“002”課程成績高的所有學生的學號；

select a.SID from (select Sid,score from SC where CID='001') a,(select Sid,score 
	from SC where CID='002') b 
	where a.score>b.score and a.Sid=b.Sid;
 

2、查詢平均成績大於60分的同學的學號和平均成績；

select SID,avg(score) 
    from sc 
    group by SID having avg(score) >60; 

3、查詢所有同學的學號、姓名、選課數、總成績；

select Student.SID,Student.Sname,count(SC.CID),sum(score) 
	from Student left Outer join SC on Student.SID=SC.SID 
	group by Student.SID,Sname 

4、查詢姓“李”的老師的個數；

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

5、查詢沒學過“葉平”老師課的同學的學號、姓名；

select Student.SID,Student.Sname 
    from Student 
where SID not in (select distinct(SC.SID) from SC,Course,Teacher 
where SC.CID=Course.CID and Teacher.TID=Course.TID and Teacher.Tname='葉平');

6、查詢學過“001”並且也學過編號“002”課程的同學的學號、姓名；

select Student.SID,Student.Sname 
	from Student,SC 
	where Student.SID=SC.SID and SC.CID='001'and exists( 
Select * from SC as SC_2 where SC_2.SID=SC.SID and SC_2.CID='002');
 

7、查詢學過“葉平”老師所教的所有課的同學的學號、姓名；

select SID,Sname 
	from Student 
	where SID in (select SID from SC ,Course ,Teacher 
			where SC.CID=Course.CID and Teacher.TID=Course.TID and Teacher.Tname='葉平' 
			group by SID having count(SC.CID)=(select count(CID) from Course,Teacher 
where Teacher.TID=Course.TID and Tname='葉平')); 

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 SID,Sname from (select Student.SID,Student.Sname,score ,(select score from SC SC_2 where SC_2.SID=Student.SID and SC_2.CID='002') score2 
	from Student,SC where Student.SID=SC.SID and CID='001') S_2 where score2 <score; 

9、查詢所有課程成績小於60分的同學的學號、姓名；

select SID,Sname 
	from Student 
	where SID not in (select Student.SID from Student,SC where S.SID=SC.SID and score>60); 
	

10、查詢沒有學全所有課的同學的學號、姓名；

select Student.SID,Student.Sname 
    from Student,SC 
    where Student.SID=SC.SID group by Student.SID,Student.Sname having count(CID) <(select count(CID) from Course); 

11、查詢至少有一門課與學號為“1001”的同學所學相同的同學的學號和姓名；

select SID,Sname from Student,SC where Student.SID=SC.SID and CID in select CID from SC where SID='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.SID,Sname 
    from Student,SC 
    where Student.SID=SC.SID and CID in (select CID from SC where SID='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(SC_2.score) 
    from SC SC_2 
where SC_2.CID=SC.CID )
from Course,Teacher where Course.CID=SC.CID and Course.TID=Teacher.TID and Teacher.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 SID from SC where CID in (select CID from SC where SID='1002') 
    group by SID having count(*)=(select count(*) from SC where SID='1002');

15、刪除學習“葉平”老師課的SC表記錄；

Delete SC 
    from course ,Teacher 
    where Course.CID=SC.CID and Course.TID= Teacher.TID 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、2號課的平均成績；

Insert SC select SID,'002',(Select avg(score) 
    from SC where CID='002') from Student where SID not in (Select SID from SC where CID='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 SID as 學生ID 
        ,(SELECT score FROM SC WHERE SC.SID=t.SID AND CID='004') AS 資料庫 
        ,(SELECT score FROM SC WHERE SC.SID=t.SID AND CID='001') AS 企業管理 
        ,(SELECT score FROM SC WHERE SC.SID=t.SID AND CID='006') AS 英語 
        ,COUNT(*) AS 有效課程數, AVG(t.score) AS 平均成績 
    FROM SC AS t 
    GROUP BY SID 
    ORDER BY avg(t.score) 

18、查詢各科成績最高和最低的分：以如下形式顯示：課程ID，最高分，最低分

 SELECT L.CID As 課程ID,L.score AS 最高分,R.score AS 最低分 
    FROM SC L ,SC AS R 
    WHERE L.CID = R.CID and 
        L.score = (SELECT MAX(IL.score) 
                      FROM SC AS IL,Student AS IM 
                      WHERE L.CID = IL.CID and IM.SID=IL.SID 
                      GROUP BY IL.CID) 
        AND 
        R.Score = (SELECT MIN(IR.score) 
                      FROM SC AS IR 
                      WHERE R.CID = IR.CID 
                  GROUP BY IR.CID 
                    ); 

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.CID 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.CID=course.CID 
    GROUP BY t.CID 
    ORDER BY 100 * SUM(CASE WHEN isnull(score,0)>=60 THEN 1 ELSE 0 END)/COUNT(*) 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）

 SELECT SUM(CASE WHEN CID ='001' THEN score ELSE 0 END)/SUM(CASE CID WHEN '001' THEN 1 ELSE 0 END) AS 企業管理平均分 
        ,100 * SUM(CASE WHEN CID = '001' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN CID = '001' THEN 1 ELSE 0 END) AS 企業管理及格百分數 
        ,SUM(CASE WHEN CID = '002' THEN score ELSE 0 END)/SUM(CASE CID WHEN '002' THEN 1 ELSE 0 END) AS 馬克思平均分 
        ,100 * SUM(CASE WHEN CID = '002' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN CID = '002' THEN 1 ELSE 0 END) AS 馬克思及格百分數 
        ,SUM(CASE WHEN CID = '003' THEN score ELSE 0 END)/SUM(CASE CID WHEN '003' THEN 1 ELSE 0 END) AS UML平均分 
        ,100 * SUM(CASE WHEN CID = '003' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN CID = '003' THEN 1 ELSE 0 END) AS UML及格百分數 
        ,SUM(CASE WHEN CID = '004' THEN score ELSE 0 END)/SUM(CASE CID WHEN '004' THEN 1 ELSE 0 END) AS 資料庫平均分 
        ,100 * SUM(CASE WHEN CID = '004' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN CID = '004' THEN 1 ELSE 0 END) AS 資料庫及格百分數 
	FROM SC

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.TID) AS 教師ID,MAX(Z.Tname) AS 教師姓名,C.CID AS 課程ＩＤ,MAX(C.Cname) AS 課程名稱,AVG(Score) AS 平均成績 
		FROM SC AS T,Course AS C ,Teacher AS Z 
		where T.CID=C.CID and C.TID=Z.TID 
	GROUP BY C.CID 
	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） 的[學生ID],[學生姓名],企業管理,馬克思,UML,資料庫,平均成績

SELECT DISTINCT top 3 
      SC.SID As 學生學號, 
        Student.Sname AS 學生姓名 , 
      T1.score AS 企業管理, 
      T2.score AS 馬克思, 
      T3.score AS UML, 
      T4.score AS 資料庫, 
      ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0) as 總分 
      FROM Student,SC LEFT JOIN SC AS T1 
                      ON SC.SID = T1.SID AND T1.CID = '001' 
            LEFT JOIN SC AS T2 
                      ON SC.SID = T2.SID AND T2.CID = '002' 
            LEFT JOIN SC AS T3 
                      ON SC.SID = T3.SID AND T3.CID = '003' 
            LEFT JOIN SC AS T4 
                      ON SC.SID = T4.SID AND T4.CID = '004' 
      WHERE student.SID=SC.SID and 
      ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0) 
      NOT IN 
      (SELECT 
            DISTINCT 
            TOP 15 WITH TIES 
            ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0) 
      FROM sc 
            LEFT JOIN sc AS T1 
                      ON sc.SID = T1.SID AND T1.CID = 'k1' 
            LEFT JOIN sc AS T2 
                      ON sc.SID = T2.SID AND T2.CID = 'k2' 
            LEFT JOIN sc AS T3 
                      ON sc.SID = T3.SID AND T3.CID = 'k3' 
            LEFT JOIN sc AS T4 
                      ON sc.SID = T4.SID AND T4.CID = 'k4' 
      ORDER BY ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0) DESC);

23、統計列印各科成績,各分數段人數:課程ID,課程名稱,[100-85],[85-70],[70-60],[ <60]

SELECT SC.CID 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.CID=Course.CID 
    GROUP BY SC.CID,Cname;

24、查詢學生平均成績及其名次

 SELECT 1+(SELECT COUNT( distinct 平均成績) 
              FROM (SELECT SID,AVG(score) AS 平均成績 
                      FROM SC 
                  GROUP BY SID 
                  ) AS T1 
            WHERE 平均成績> T2.平均成績) as 名次, 
      SID as 學生學號,平均成績 
    FROM (SELECT SID,AVG(score) 平均成績 
            FROM SC 
        GROUP BY SID 
        ) AS T2 
    ORDER BY 平均成績desc;

25、查詢各科成績前三名的記錄:(不考慮成績並列情況)

 SELECT t1.SID as 學生ID,t1.CID as 課程ID,Score as 分數 
      FROM SC t1 
      WHERE score IN (SELECT TOP 3 score 
              FROM SC 
              WHERE t1.CID= CID 
            ORDER BY score DESC 
              ) 
      ORDER BY t1.CID; 

26、查詢每門課程被選修的學生數

select Cid,count(SID) from sc group by CID;

27、查詢出只選修了一門課程的全部學生的學號和姓名

select SC.SID,Student.Sname,count(CID) AS 選課數 
	from SC ,Student 
	where SC.SID=Student.SID group by SC.SID ,Student.Sname having count(CID)=1; 

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'；

29、查詢姓“張”的學生名單

 SELECT Sname FROM Student WHERE Sname like '張%'; 

30、查詢同名同性學生名單，並統計同名人數

select Sname,count(*) from Student group by Sname having 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、查詢每門課程的平均成績，結果按平均成績升序排列，平均成績相同時，按課程號降序排列

 Select CID,Avg(score) from SC group by CID order by Avg(score),CID DESC ; 

33、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.SID ,avg(score) 
    from Student,SC 
    where Student.SID=SC.SID group by SC.SID,Sname having    avg(score)>85; 

34、查詢課程名稱為“資料庫”，且分數低於60的學生姓名和分數

 Select Sname,isnull(score,0) 
    from Student,SC,Course 
    where SC.SID=Student.SID and SC.CID=Course.CID and Course.Cname='資料庫'and score <60;

35、查詢所有學生的選課情況；

SELECT SC.SID,SC.CID,Sname,Cname 
    FROM SC,Student,Course 
    where SC.SID=Student.SID and SC.CID=Course.CID ; 

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.SID,student.Sname,SC.CID,SC.score 
    FROM student,Sc 
    WHERE SC.score>=70 AND SC.SID=student.SID; 

37、查詢不及格的課程，並按課程號從大到小排列

select Cid from sc where scor e <60 order by CID ; 

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.SID,Student.Sname from SC,Student where SC.SID=Student.SID and Score>80 and CID='003';

39、求選了課程的學生人數

select count(*) from sc; 

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,CourseC,Teacher 
    where Student.SID=SC.SID and SC.CID=C.CID and C.TID=Teacher.TID and Teacher.Tname='葉平' and SC.score=(select max(score)from SC where CID=C.CID );

41、查詢各個課程及相應的選修人數

select count(*) from sc group by CID; 

42、查詢不同課程成績相同的學生的學號、課程號、學生成績

select distinct A.SID,B.score from SC A ,SC B where A.Score=B.Score and A.CID <>B.CID ;

43、查詢每門功成績最好的前兩名

SELECT t1.SID as 學生ID,t1.CID as 課程ID,Score as 分數 
      FROM SC t1 
      WHERE score IN (SELECT TOP 2 score 
              FROM SC 
              WHERE t1.CID= CID 
            ORDER BY score DESC 
              ) 
      ORDER BY t1.CID;

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列，查詢結果按人數降序排列，若人數相同，按課程號升序排列

select CID as 課程號,count(*) as 人數 
    from sc 
    group by CID 
    order by count(*) desc,Cid

45、檢索至少選修兩門課程的學生學號

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

46、查詢全部學生都選修的課程的課程號和課程名

select CID,Cname 
    from Course 
    where CID in (select Cid from sc group by Cid)

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 SID not in (select SID from Course,Teacher,SC where Course.TID=Teacher.TID and SC.CID=course.CID and Tname='葉平'); 

48、查詢兩門以上不及格課程的同學的學號及其平均成績

 select SID,avg(isnull(score,0)) from SC where SID in (select SID from SC where score <60 group by SID having count(*)>2)group by SID;