SQL查询案例

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如下数据库表:

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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：课程名称
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

  1. 查询“001”课程比“002”课程成绩高的所有学生的学号

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    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

  2. 查询平均成绩大于60分的同学的学号和平均成绩

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    查询平均成绩大于60分的同学的学号和平均成绩

  3. 查询所有同学的学号、姓名、选课数、总成绩

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    select student.S#, student.Sname, count(sc.C#), sum(score) from student left outer join SC on student.S# = SC.S# group by S

  4. 查询姓‘李’的老师的个数

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

  5. 查询没有学过“叶平”老师可的同学的学号、姓名：

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    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 Teahcer.Tname ='叶平');

  6. 查询学过“叶平”老师所教的所有课的同学的学号、姓名：

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    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'));

  7. 查询学过“011”并且也学过编号“002”课程的同学的学号、姓名：

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    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');

  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：

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    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的同学的学号、姓名：

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    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：

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    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”同学所学相同的同学的学号和姓名：

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    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；

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    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：

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    Update Sc Set Score=(Select Avg(s2_Score) From sc s2 Where s2.c#=sc.c#)  
    Where c# IN
    (Select c# From sc cs INNER JOIN Teacher tc ON cs.t#=tc.t# WHERE 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：

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    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：

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    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、002号课的平均成绩：

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    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：

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    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 平局成绩
    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： 以如下的形式显示：课程ID，最高分，最低分

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    select L.c# as 课程ID, L.score as 最高分,
    R.score as 最低分
    from sc L, sc R
    where L.c# = R.c#
    and L.score = (select max(IL.score)
            from sc 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：

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    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）：

  21. 查询不同老师所教不同课程平均分从高到低显示：

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    SELECT max(Z.T#) AS 教师ID,
    MAX(Z.Tname) AS 教师姓名,
    C.C# AS 课程ID,
    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)：

  23. 统计下列各科成绩，各分数段人数：课程ID，课程名称，[100-85],[85-70],[70-60],[ 小于60] ：

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    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：

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    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）：

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    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)
    ```        
    26. 查询每门课程被选修的学生数：

select c#, count(s#) from sc group by c#;

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27. 查询出只选修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;

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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’;

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29. 查询姓“张”的学生名单：

select sname from student where sname like ‘张%’;

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30. 查询同名同姓的学生名单，并统计同名人数：

select sanme,count() from student group by sname havang count()>1;

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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’;

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32. 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;

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33. 查询每门课程的平均成绩，结果按平均成绩升序排序，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;

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34. 查询课程名称为“数据库”，且分数低于60的学生名字和分数：

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;

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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#;

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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#;

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37. 查询不及格的课程，并按课程号从大到小的排列：

select c# from sc where score<60 order by c#;

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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’;

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39. 求选了课程的学生人数：

select count(*) from sc;

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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#);

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41. 查询各个课程及相应的选修人数：

select count(*) from sc group by c#;

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42. 查询不同课程成绩相同的学生和学号、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#;

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43. 查询每门课程成绩最好的前两名：

select t1.s# as 学生ID,t1.c# 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#;

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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序，若人数相同，按课程号升序排序：

select c# as 课程号,count() as 人数 from sc group by c# order by count() desc c#;

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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;

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46. 查询全部学生选修的课程和课程号和课程名：

select c# ,cname from course where c# in (select c# from sc group by c#);

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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’);

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48. 查询两门以上不及格课程的同学的学号以及其平均成绩：

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#;

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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;

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50. 删除“002”同学的“001”课程的成绩：

delect from sc where s#=’002’ and c#=’001’;

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