常用sql语句练习-2

21、查询不同老师所教不同课程平均分从高到低显示
  SELECT max(Z.T) AS 教师ID,MAX(Z.Tname) AS 教师姓名,C.C AS 课程ＩＤ,MAX(C.Cname) AS 课程名称,AVG(Score) AS 平均成绩
    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、查询如下课程成绩第 3 名到第 6 名的学生成绩单：企业管理（001），马克思（002），UML （003），数据库（004）
    [学生ID],[学生姓名],企业管理,马克思,UML,数据库,平均成绩
    SELECT  DISTINCT top 3
      SC.S As 学生学号,
        Student.Sname AS 学生姓名 ,
      T1.score AS 企业管理,
      T2.score AS 马克思,
      T3.score AS UML,
      T4.score AS 数据库,
      ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0) as 总分
      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、统计列印各科成绩,各分数段人数:课程ID,课程名称,[100-85],[85-70],[70-60],[ <60]
    SELECT SC.C as 课程ID, Cname as 课程名称
        ,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、查询学生平均成绩及其名次
      SELECT 1+(SELECT COUNT( distinct 平均成绩)
              FROM (SELECT S,AVG(score) AS 平均成绩
                      FROM SC
                  GROUP BY S 
                  ) AS T1
            WHERE 平均成绩 > T2.平均成绩) as 名次,
      S as 学生学号,平均成绩
    FROM (SELECT S,AVG(score) 平均成绩
            FROM SC
        GROUP BY S 
        ) AS T2
    ORDER BY 平均成绩 desc;
 
25、查询各科成绩前三名的记录:(不考虑成绩并列情况)
      SELECT t1.S as 学生ID,t1.C as 课程ID,Score as 分数
      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、查询每门课程被选修的学生数
  select c,count(S) from sc group by C;
27、查询出只选修了一门课程的全部学生的学号和姓名
  select SC.S,Student.Sname,count(C) AS 选课数
  from SC ,Student
  where SC.S=Student.S group by SC.S ,Student.Sname having count(C)=1;
28、查询男生、女生人数
    Select count(Ssex) as 男生人数 from Student group by Ssex having Ssex='男';
    Select count(Ssex) as 女生人数 from Student group by Ssex having Ssex='女'；
29、查询姓“张”的学生名单
    SELECT Sname FROM Student WHERE Sname like '张%';
30、查询同名同性学生名单，并统计同名人数
  select Sname,count(*) from Student group by Sname having  count(*)>1;;
31、1981年出生的学生名单(注：Student表中Sage列的类型是datetime)
    select Sname,  CONVERT(char (11),DATEPART(year,Sage)) as age
    from student
    where  CONVERT(char(11),DATEPART(year,Sage))='1981';
32、查询每门课程的平均成绩，结果按平均成绩升序排列，平均成绩相同时，按课程号降序排列
    Select C,Avg(score) from SC group by C order by Avg(score),C DESC ;
33、查询平均成绩大于85的所有学生的学号、姓名和平均成绩
    select Sname,SC.S ,avg(score)
    from Student,SC
    where Student.S=SC.S group by SC.S,Sname having    avg(score)>85;
34、查询课程名称为“数据库”，且分数低于60的学生姓名和分数
    Select Sname,isnull(score,0)
    from Student,SC,Course
    where SC.S=Student.S and SC.C=Course.C and  Course.Cname='数据库'and score <60;
35、查询所有学生的选课情况；
    SELECT SC.S,SC.C,Sname,Cname
    FROM SC,Student,Course
    where SC.S=Student.S and SC.C=Course.C ;
36、查询任何一门课程成绩在70分以上的姓名、课程名称和分数；
    SELECT  distinct student.S,student.Sname,SC.C,SC.score
    FROM student,Sc
    WHERE SC.score>=70 AND SC.S=student.S;
37、查询不及格的课程，并按课程号从大到小排列
    select c from sc where scor e <60 order by C ;
38、查询课程编号为003且课程成绩在80分以上的学生的学号和姓名；
    select SC.S,Student.Sname from SC,Student where SC.S=Student.S and Score>80 and C='003';
39、求选了课程的学生人数
    select count(*) from sc;
40、查询选修“叶平”老师所授课程的学生中，成绩最高的学生姓名及其成绩
    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='叶平' and SC.score=(select max(score)from SC where C=C.C );
41、查询各个课程及相应的选修人数
    select count(*) from sc group by C;
42、查询不同课程成绩相同的学生的学号、课程号、学生成绩
  select distinct  A.S,B.score from SC A  ,SC B where A.Score=B.Score and A.C <>B.C ;
43、查询每门功成绩最好的前两名
    SELECT t1.S as 学生ID,t1.C as 课程ID,Score as 分数
      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、统计每门课程的学生选修人数（超过10人的课程才统计）。要求输出课程号和选修人数，查询结果按人数降序排列，查询结果按人数降序排列，若人数相同，按课程号升序排列 
    select  C as 课程号,count(*) as 人数
    from  sc 
    group  by  C 
    order  by  count(*) desc,c 
45、检索至少选修两门课程的学生学号
    select  S  
    from  sc 
    group  by  s 
    having  count(*)  >  =  2
46、查询全部学生都选修的课程的课程号和课程名
    select  C,Cname 
    from  Course 
    where  C  in  (select  c  from  sc group  by  c) 
47、查询没学过“叶平”老师讲授的任一门课程的学生姓名
    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='叶平');
48、查询两门以上不及格课程的同学的学号及其平均成绩
    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、检索“004”课程分数小于60，按分数降序排列的同学学号
    select S from SC where C='004'and score <60 order by score desc;
50、删除“002”同学的“001”课程的成绩
delete from Sc where S='001'and C='001';