sql 经典面试题及答案(选课表)

Student(Sno,Sname,Sage,Ssex) 学生表       Sno：学号；Sname：学生姓名；Sage：学生年龄；Ssex：学生性别
Course(Cno,Cname,Tno) 课程表                    Cno,课程编号；Cname：课程名字；Tno：教师编号
SC(Sno,Cno,score) 成绩表                             Sno：学号；Cno,课程编号；score：成绩
Teacher(Tno,Tname) 教师表                        Tno：教师编号； Tname：教师名字

 

创建数据表：

create table Student(

Sno varchar(10) not null primary key,

Sname varchar(20) null,

Sage int null,

Ssex varchar(2) null

)

create table Course(

Cno varchar(10) not null primary key,

Cname varchar(20) null,

Tno varchar(20) null

)

create table SC(

Sno varchar(10) not null primary key,

Cno varchar(10) not null primary key,

score int null

)

create table Teacher(

Tno varchar(20) primary key not null,

Tname varchar(20) null

)

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.Sno from (select Sno,score from SC where Cno='001') a,(select Sno,score
  from SC where Cno='002') b
  where a.score>b.score and a.Sno=b.Sno;
2、查询平均成绩大于60分的同学的学号和平均成绩；
    select Sno,avg(score)
    from sc
    group by Sno having avg(score) >60;
3、查询所有同学的学号、姓名、选课数、总成绩；
  select Student.Sno,Student.Sname,count(SC.Cno),sum(score)
  from Student left Outer join SC on Student.Sno=SC.Sno
  group by Student.Sno,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.Sno,Student.Sname
    from Student 
    where Sno not in (select distinct( SC.Sno) from SC,Course,Teacher where SC.Cno=Course.Cno and Teacher.Tno=Course.Tno  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.Sno,Student.Sname from Student,SC where Student.Sno=SC.Sno and SC.Cno='001'and exists( Select * from SC as SC_2 where SC_2.Sno=SC.Sno and SC_2.Cno='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 Sno,Sname
  from Student
  where Sno in (select Sno from SC ,Course ,Teacher where SC.Cno=Course.Cno and Teacher.Tno=Course.Tno and Teacher.Tname='叶平' group by Sno having count(SC.Cno)=(select count(Cno) from Course,Teacher  where Teacher.Tno=Course.Tno 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 Sno,Sname from (select Student.Sno,Student.Sname,score ,(select score from SC SC_2 where SC_2.Sno=Student.Sno and SC_2.Cno='002') score2
  from Student,SC where Student.Sno=SC.Sno and Cno='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 Sno,Sname
  from Student
  where Sno not in (select Student.Sno from Student,SC where S.Sno=SC.Sno and score>60);
10、查询没有学全所有课的同学的学号、姓名；
    select Student.Sno,Student.Sname
    from Student,SC
    where Student.Sno=SC.Sno group by  Student.Sno,Student.Sname having count(Cno) <(select count(Cno) 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 Sno,Sname from Student,SC where Student.Sno=SC.Sno and Cno in select Cno from SC where Sno='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.Sno,Sname
    from Student,SC
    where Student.Sno=SC.Sno and Cno in (select Cno from SC where Sno='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.Cno=SC.Cno ) from Course,Teacher where Course.Cno=SC.Cno and Course.Tno=Teacher.Tno 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 Sno from SC where Cno in (select Cno from SC where Sno='1002')
    group by Sno having count(*)=(select count(*) from SC where Sno='1002');
15、删除学习“叶平”老师课的SC表记录；
    Delect SC
    from course ,Teacher 
    where Course.Cno=SC.Cno and Course.Tno= Teacher.Tno 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 Sno,'002',(Select avg(score)
    from SC where Cno='002') from Student where Sno not in (Select Sno from SC where Cno='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 Sno as 学生ID
        ,(SELECT score FROM SC WHERE SC.Sno=t.Sno AND Cno='004') AS 数据库
        ,(SELECT score FROM SC WHERE SC.Sno=t.Sno AND Cno='001') AS 企业管理
        ,(SELECT score FROM SC WHERE SC.Sno=t.Sno AND Cno='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 Sno
    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.Cno As 课程ID,L.score AS 最高分,R.score AS 最低分
    FROM SC L ,SC AS R
    WHERE L.Cno = R.Cno and
        L.score = (SELECT MAX(IL.score)
                      FROM SC AS IL,Student AS IM
                      WHERE L.Cno = IL.Cno and IM.Sno=IL.Sno
                      GROUP BY IL.Cno)
        AND
        R.Score = (SELECT MIN(IR.score)
                      FROM SC AS IR
                      WHERE R.Cno = IR.Cno
                  GROUP BY IR.Cno
                    );
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.Cno 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.Cno=course.Cno
    GROUP BY t.Cno
    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 Cno ='001' THEN score ELSE 0 END)/SUM(CASE Cno WHEN '001' THEN 1 ELSE 0 END) AS 企业管理平均分
        ,100 * SUM(CASE WHEN Cno = '001' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN Cno = '001' THEN 1 ELSE 0 END) AS 企业管理及格百分数
        ,SUM(CASE WHEN Cno = '002' THEN score ELSE 0 END)/SUM(CASE Cno WHEN '002' THEN 1 ELSE 0 END) AS 马克思平均分
        ,100 * SUM(CASE WHEN Cno = '002' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN Cno = '002' THEN 1 ELSE 0 END) AS 马克思及格百分数
        ,SUM(CASE WHEN Cno = '003' THEN score ELSE 0 END)/SUM(CASE Cno WHEN '003' THEN 1 ELSE 0 END) AS UML平均分
        ,100 * SUM(CASE WHEN Cno = '003' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN Cno = '003' THEN 1 ELSE 0 END) AS UML及格百分数
        ,SUM(CASE WHEN Cno = '004' THEN score ELSE 0 END)/SUM(CASE Cno WHEN '004' THEN 1 ELSE 0 END) AS 数据库平均分
        ,100 * SUM(CASE WHEN Cno = '004' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN Cno = '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.Tno) AS 教师ID,MAX(Z.Tname) AS 教师姓名,C.Cno 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.Cno=C.Cno and C.Tno=Z.Tno
  GROUP BY C.Cno
  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.Sno 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.Sno = T1.Sno AND T1.Cno = '001'
            LEFT JOIN SC AS T2
                      ON SC.Sno = T2.Sno AND T2.Cno = '002'
            LEFT JOIN SC AS T3
                      ON SC.Sno = T3.Sno AND T3.Cno = '003'
            LEFT JOIN SC AS T4
                      ON SC.Sno = T4.Sno AND T4.Cno = '004'
      WHERE student.Sno=SC.Sno 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.Sno = T1.Sno AND T1.Cno = 'k1'
            LEFT JOIN sc AS T2
                      ON sc.Sno = T2.Sno AND T2.Cno = 'k2'
            LEFT JOIN sc AS T3
                      ON sc.Sno = T3.Sno AND T3.Cno = 'k3'
            LEFT JOIN sc AS T4
                      ON sc.Sno = T4.Sno AND T4.Cno = '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.Cno 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.Cno=Course.Cno
    GROUP BY SC.Cno,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 Sno,AVG(score) AS 平均成绩
                      FROM SC
                  GROUP BY Sno
                  ) AS T1
            WHERE 平均成绩 > T2.平均成绩) as 名次,
      Sno as 学生学号,平均成绩
    FROM (SELECT Sno,AVG(score) 平均成绩
            FROM SC
        GROUP BY Sno
        ) 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.Sno as 学生ID,t1.Cno as 课程ID,Score as 分数
      FROM SC t1
      WHERE score IN (SELECT TOP 3 score
              FROM SC
              WHERE t1.Cno= Cno
            ORDER BY score DESC
              )
      ORDER BY t1.Cno;
26、查询每门课程被选修的学生数
  select Cno,count(Sno) from sc group by Cno;
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.Sno,Student.Sname,count(Cno) AS 选课数
  from SC ,Student
  where SC.Sno=Student.Sno group by SC.Sno ,Student.Sname having count(Cno)=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 Cno,Avg(score) from SC group by Cno order by Avg(score),Cno 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.Sno ,avg(score)
    from Student,SC
    where Student.Sno=SC.Sno group by SC.Sno,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.Sno=Student.Sno and SC.Cno=Course.Cno and  Course.Cname='数据库'and score <60;
35、查询所有学生的选课情况；
    SELECT SC.Sno,SC.Cno,Sname,Cname
    FROM SC,Student,Course
    where SC.Sno=Student.Sno and SC.Cno=Course.Cno ;
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.Sno,student.Sname,SC.Cno,SC.score
    FROM student,Sc
    WHERE SC.score>=70 AND SC.Sno=student.Sno;
37、查询不及格的课程，并按课程号从大到小排列
    select Cno from sc where scor e <60 order by Cno ;
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.Sno,Student.Sname from SC,Student where SC.Sno=Student.Sno and Score>80 and Cno='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.Sno=SC.Sno and SC.Cno=C.Cno and C.Tno=Teacher.Tno and Teacher.Tname='叶平' and SC.score=(select max(score)from SC where Cno=C.Cno );
41、查询各个课程及相应的选修人数
    select count(*) from sc group by Cno;
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.Sno,B.score from SC A  ,SC B where A.Score=B.Score and A.Cno <>B.Cno ;
43、查询每门功成绩最好的前两名
    SELECT t1.Sno as 学生ID,t1.Cno as 课程ID,Score as 分数
      FROM SC t1
      WHERE score IN (SELECT TOP 2 score
              FROM SC
              WHERE t1.Cno= Cno
            ORDER BY score DESC
              )
      ORDER BY t1.Cno;
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  Cno as 课程号,count(*) as 人数
    from  sc 
    group  by  Cno
    order  by  count(*) desc,Cno 
45、检索至少选修两门课程的学生学号
    select  Sno 
    from  sc 
    group  by  Sno
    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  Cno,Cname 
    from  Course 
    where  Cno  in  (select  Cno  from  sc group  by  Cno) 
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 Sno not in (select Sno from Course,Teacher,SC where Course.Tno=Teacher.Tno and SC.Cno=course.Cno 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 Sno,avg(isnull(score,0)) from SC where Sno in (select Sno from SC where score <60 group by Sno having count(*)>2)group by Sno;
49、检索“004”课程分数小于60，按分数降序排列的同学学号
    select Sno from SC where Cno='004'and score <60 order by score desc;