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50条SQL查询技巧

发布时间:2015年05月30日 评论数:抢沙发 阅读数:1152

    Course(C#,Cname,T#) 课程表
    SC(S#,C#,score) 成绩表
    Teacher(T#,Tname) 教师表
     
    问题:
    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# = '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';

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本文作者:Mr.linus      文章标题: 50条SQL查询技巧
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