数据库基本操作

一、数据表 Student(S#,Sname,Sage,Ssex) 学生表 S#：学号；Sname：学生姓名；Sage：学生年龄；Ssex：学生性别 Course(C#,Cname,T#) 课程表 C#,课程编号；Cname：课程名字；T#：教师编号 SC(S#,C#,score) 成绩表 S#：学号；C#,课程编号；score：成绩 Teacher(

一、数据表 Student(S#,Sname,Sage,Ssex) 学生表 S#：学号；Sname：学生姓名；Sage：学生年龄；Ssex：学生性别
Course(C#,Cname,T#) 课程表 C#,课程编号；Cname：课程名字；T#：教师编号
SC(S#,C#,score) 成绩表 S#：学号；C#,课程编号；score：成绩
Teacher(T#,Tname) 教师表 T#：教师编号； Tname：教师名字

二、基本操作：
1、查询“001”课程比“002”课程成绩高的所有学生的学号；

      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、查询平均成绩大于60分的同学的学号和平均成绩；

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

3、查询所有同学的学号、姓名、选课数、总成绩；

      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、查询姓“李”的老师的个数；

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

5、查询没学过“叶平”老师课的同学的学号、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 Teacher.Tname='叶平');

6、查询学过“001”并且也学过编号“002”课程的同学的学号、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');

7、查询学过“叶平”老师所教的所有课的同学的学号、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='叶平' group by S# having count(SC.C#)=(select count(C#) from Course,Teacher  where Teacher.T#=Course.T# and Tname='叶平'));

8、查询课程编号“002”的成绩比课程编号“001”课程低的所有同学的学号、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 
9、查询所有课程成绩小于60分的同学的学号、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、查询没有学全所有课的同学的学号、姓名；
       select Student.S#,Student.Sname
       from Student,SC
       where Student.S#=SC.S# group by  Student.S#,Student.Sname having count(C#) 
11、查询至少有一门课与学号为“1001”的同学所学相同的同学的学号和姓名；
       select S#,Sname from Student,SC where Student.S#=SC.S# and C# in select C# from SC where S#='1001';
12、查询至少学过学号为“001”同学所有一门课的其他同学学号和姓名；
       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“叶平”老师教的课的成绩都更改为此课程的平均成绩；
       update SC set score=(select avg(SC_2.score)
       from SC SC_2
       where SC_2.C#=SC.C# ) from Course,Teacher where Course.C#=SC.C# and Course.T#=Teacher.T# and Teacher.Tname='叶平');
14、查询和“1002”号的同学学习的课程完全相同的其他同学学号和姓名；
       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、删除学习“叶平”老师课的SC表记录；
       Delect SC
       from course ,Teacher 
       where Course.C#=SC.C# and Course.T#= Teacher.T# and Tname='叶平';
16、向SC表中插入一些记录，这些记录要求符合以下条件：没有上过编号“003”课程的同学学号、2、号课的平均成绩；
       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、按平均成绩从高到低显示所有学生的“数据库”、“企业管理”、“英语”三门的课程成绩，按如下形式显示： 学生ID,,数据库,企业管理,英语, 有效课程数,有效平均分
        SELECT S# as 学生ID
           ,(SELECT score FROM SC WHERE SC.S#=t.S# AND C#='004') AS 数据库
           ,(SELECT score FROM SC WHERE SC.S#=t.S# AND C#='001') AS 企业管理
           ,(SELECT score FROM SC WHERE SC.S#=t.S# AND C#='006') AS 英语
           ,COUNT(*) AS 有效课程数, AVG(t.score) AS 平均成绩
        FROM SC AS t
        GROUP BY S#
        ORDER BY avg(t.score) 
18、查询各科成绩最高和最低的分：以如下形式显示：课程ID，最高分，最低分
       SELECT L.C# As 课程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 AS 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#
                    );
19、按各科平均成绩从低到高和及格率的百分数从高到低顺序
        SELECT t.C# AS 课程号,max(course.Cname)AS 课程名,isnull(AVG(score),0) AS 平均成绩
           ,100 * SUM(CASE WHEN  isnull(score,0)>=60 THEN 1 ELSE 0 END)/COUNT(*) AS 及格百分数
        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、查询如下课程平均成绩和及格率的百分数(用"1行"显示): 企业管理（001），马克思（002），OO&UML （003），数据库（004）
       SELECT SUM(CASE WHEN C# ='001' THEN score ELSE 0 END)/SUM(CASE C# WHEN '001' THEN 1 ELSE 0 END) AS 企业管理平均分
            ,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 企业管理及格百分数
            ,SUM(CASE WHEN C# = '002' THEN score ELSE 0 END)/SUM(CASE C# WHEN '002' THEN 1 ELSE 0 END) AS 马克思平均分
            ,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 马克思及格百分数
            ,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及格百分数
            ,SUM(CASE WHEN C# = '004' THEN score ELSE 0 END)/SUM(CASE C# WHEN '004' THEN 1 ELSE 0 END) AS 数据库平均分
            ,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 数据库及格百分数
      FROM SC
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],[ 
       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 
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 
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 
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 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 
50、删除“002”同学的“001”课程的成绩
      delete from Sc where S#='002'and C#='001';