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 <score;

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#) <(select count(C#) from Course);

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<i>本文来源gaodai$ma#com搞$$代**码)网@</i># = '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);

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