一般面試時考SQL，主要就是考你“統計分析”這一塊，下面我們來看面試官經常採用的手段。


由4張簡單的不能再簡單的表，演變出50道SQL


哈哈哈哈，夠這個面試官面個15，20個人，不帶重複的了，而且每個SQL你真的不動動腦子還寫不出呢，你別不服氣，下面開始。

表結構：



表Student

(S#,Sname,Sage,Ssex) 學生表 


S#	 student_no 

Sage	student_age

Ssex	student_sex 
 


表Course

(C#,Cname,T#) 課程表


C#	 course_no 

Cname 	 course_name 

T# 	 teacher_no 






表SC（學生與課程的分數mapping 表）

(S#,C#,score) 成績表 


S# 	student_no 
C# 	course_no 
score 	分數啦 






表Teacher

(T#,Tname) 教師表 


T# 	teacher_no 
Tname 	teacher_name 






50道問題開始






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') 




  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#,Student.Sname,count(SC.C#),sum(score) 

  from Student left Outer join SC on Student.S#=SC.S#

  group by Student.S#,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.S#,Student.Sname 

    from Student  

    where S# not in (select distinct( SC.S#) fromSC,Course,Teacher where  SC.C#=Course.C#and Teacher.T#=Course.T# andTeacher.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.S#,Student.Sname fromStudent,SC where Student.S#=SC.S# andSC.C#='001'and exists( Select * from SC as SC_2 where SC_2.S#=SC.S# and SC_2.C#='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 S#,Sname 

  from Student 

  where S# in (select S# from SC,Course ,Teacher where SC.C#=Course.C# andTeacher.T#=Course.T# and Teacher.Tname='葉平'group by S# having count(SC.C#)=(select count(C#) fromCourse,Teacher  whereTeacher.T#=Course.T# 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 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# andC#='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 S#,Sname 

  from Student 

  where S# not in (select Student.S# fromStudent,SC where S.S#=SC.S# andscore>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 
    whereStudent.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”的同學所學相同的同學的學號和姓名； 


    select S#,Sname from Student,SC whereStudent.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(SC_2.score) 

    from SC SC_2 

    where SC_2.C#=SC.C# ) fromCourse,Teacher where Course.C#=SC.C# andCourse.T#=Teacher.T# 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 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'); 




15、刪除學習“葉平”老師課的SC表記錄； 

    DelectSC 

    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、2號課的平均成績； 

    Insert SC select S#,'002',(Select avg(score) 

    from SC where C#='002') from Student where S# notin (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# as 學生ID 

        ,(SELECT score FROM SC WHERE SC.S#=t.S#AND C#='004') AS 資料庫 

        ,(SELECT score FROM SC WHERE SC.S#=t.S#AND C#='001') AS 企業管理 

        ,(SELECT score FROM SC WHERE SC.S#=t.S#AND C#='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 S# 

    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.C# As 課程ID,L.score AS 最高分,R.score AS 最低分 

    FROM SC L ,SC AS R 

    WHERE L.C# = R.C# and 

       L.score = (SELECT MAX(IL.score) 

                      FROM SC ASIL,Student AS IM 

                      WHERE L.C# =IL.C# and IM.S#=IL.S# 

                      GROUP BYIL.C#) 

        AND

        R.Score= (SELECT MIN(IR.score) 

                      FROM SC ASIR 

                      WHERE R.C# =IR.C# 

                 GROUP BY IR.C# 

                    ); 




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 


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 C# ='001' THEN score ELSE 0 END)/SUM(CASE C# WHEN '001' THEN 1 ELSE 0 END) AS 企業管理平均分 

        ,100 * SUM(CASE WHEN C# = '001' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN C# = '001' THEN 1 ELSE 0 END) AS 企業管理及格百分數 

        ,SUM(CASE WHEN C# = '002' THEN score ELSE 0 END)/SUM(CASE C# WHEN '002' THEN 1 ELSE 0 END) AS 馬克思平均分 

        ,100 * SUM(CASE WHEN C# = '002' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN C# = '002' THEN 1 ELSE 0 END) AS 馬克思及格百分數 

        ,SUM(CASE WHEN C# = '003' THEN score ELSE 0 END)/SUM(CASE C# WHEN '003' THEN 1 ELSE 0 END) AS UML平均分 

        ,100* SUM(CASE WHEN C# = '003' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN C# = '003' THEN 1 ELSE 0 END) AS UML及格百分數 

        ,SUM(CASE WHEN C# = '004' THEN score ELSE 0 END)/SUM(CASE C# WHEN '004' THEN 1 ELSE 0 END) AS 資料庫平均分 

        ,100 * SUM(CASE WHEN C# = '004' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN C# = '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.T#) AS 教師ID,MAX(Z.Tname) AS 教師姓名,C.C# 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.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） 

[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.S# 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.S# = T1.S# AND T1.C# = '001' 
            LEFT JOIN SC AS T2 
                      ON SC.S# = T2.S# AND T2.C# = '002' 
            LEFT JOIN SC AS T3 
                      ON SC.S# = T3.S# AND T3.C# = '003' 
            LEFT JOIN SC AS T4 
                      ON SC.S# = T4.S# AND T4.C# = '004' 
      WHERE student.S#=SC.S# 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.S# = T1.S# AND T1.C# = 'k1' 
            LEFT JOIN sc AS T2 
                      ON sc.S# = T2.S# AND T2.C# = 'k2' 
            LEFT JOIN sc AS T3 
                      ON sc.S# = T3.S# AND T3.C# = 'k3' 
            LEFT JOIN sc AS T4 
                      ON sc.S# = T4.S# AND T4.C# = '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.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; 
 
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; 
  
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 
              ) 
      ORDER BY t1.C#; 

26、查詢每門課程被選修的學生數 
  select c#,count(S#) from sc group by C#; 

27、查詢出只選修了一門課程的全部學生的學號和姓名 
  select SC.S#,Student.Sname,count(C#) AS 選課數 
  from SC ,Student 
  where SC.S#=Student.S# group by SC.S# ,Student.Sname having count(C#)=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 C#,Avg(score) from SC group by C# order by Avg(score),C# 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.S# ,avg(score) 
    from Student,SC 
    where Student.S#=SC.S# group by SC.S#,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.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、查詢不及格的課程，並按課程號從大到小排列 
    select c# from sc where scor e <60 order by C# ;
 
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; 
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# ); 

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的學號、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# ; 

43、查詢每門功成績最好的前兩名 
    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 2 score 
              FROM SC 
              WHERE t1.C#= C# 
            ORDER BY score DESC 
              ) 
      ORDER BY t1.C#; 

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  C# as 課程號,count(*) as 人數 
    from  sc  
    group  by  C# 
    order  by  count(*) desc,c#  

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、查詢全部學生都選修的課程的課程號和課程名 
    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'); 

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 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#; 

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 
delete from Sc where S#='001'and C#='001';