一、数据字典：
学生表：Student
ID Sid   Sname   Sage   Ssex
1    1     学生甲   14     男
2    2     学生乙   15     女
3    3     学生丙   18     男
4    4     学生丁   16     女

教师表：Teacher
ID Tid     Tname
1    1     教师甲
2    2     教师乙
3    3     教师丙
4    4     教师丁

课程表：Course
ID Cid      Cname    Tid
1    1        语文     1
2    2        数学     3
3    3        外语     4
4    4        历史     2

成绩表：SC
ID   Sid Cid Score
1     1    1     60
2     2    1     85
3     3    1     75
4     4    1     96

二、实际应用：
1、查询“语文”课程比“数学”课程成绩高的所有学生的学号；
select a.Sid from (select sid,score from SC where Cid='语文') a,(select sid,score
from SC where Cid='数学') b
where a.score>b.score and a.sid=b.sid;

2、查询平均成绩大于60分的同学的学号和平均成绩；
    select Sid,avg(score)
    from sc
    group by Sid having avg(score) >60;

3、查询所有同学的学号、姓名、选课数、总成绩；
select Student.Sid,Student.Sname,count(SC.Cid),sum(score)
from Student left Outer join SC on Student.Sid=SC.Sid
group by Student.Sid,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.Sid,Student.Sname
    from Student
    where Sid not in (select distinct( SC.Sid) from SC,Course,Teacher where SC.Cid=Course.Cid and Teacher.Tid=Course.Tid 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.Sid,Student.Sname from Student,SC where Student.Sid=SC.Sid and SC.Cid='001'and exists( Select * from SC as SC_2 where SC_2.Sid=SC.Sid and SC_2.Cid='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 Sid,Sname
from Student
where Sid in (select Sid from SC ,Course ,Teacher where SC.Cid=Course.Cid and Teacher.Tid=Course.Tid and Teacher.Tname='叶平' group by Sid having count(SC.Cid)=(select count (Cid) from Course,Teacher where Teacher.Tid=Course.Tid 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 Sid,Sname from (select Student.Sid,Student.Sname,score ,(select score from SC SC_2 where SC_2.Sid=Student.Sid and SC_2.Cid='002') score2
from Student,SC where Student.Sid=SC.Sid and Cid='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 Sid,Sname
from Student
where Sid not in (select Student.Sid from Student,SC where S.Sid=SC.Sid and score>60);

10、查询没有学全所有课的同学的学号、姓名；
    select Student.Sid,Student.Sname
    from Student,SC
    where Student.Sid=SC.Sid group by Student.Sid,Student.Sname having count(Cid) <(select count(Cid) 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 Sid,Sname from Student,SC where Student.Sid=SC.Sid and Cid in select Cid from SC where Sid='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.Sid,Sname
    from Student,SC
    where Student.Sid=SC.Sid and Cid in (select Cid from SC where Sid='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.Cid=SC.Cid ) from Course,Teacher where Course.Cid=SC.Cid and Course.Tid=Teacher.Tid and Teacher.Tname='叶平');

14、查询和“1002”号的同学学习的课程xx相同的其他同学学号和姓名；
    select Sid from SC where Cid in (select Cid from SC where Sid='1002')
    group by Sid having count(*)=(select count(*) from SC where Sid='1002');

15、删除学习“叶平”老师课的SC表记录；
    Delect SC
    from course ,Teacher
    where Course.Cid=SC.Cid and Course.Tid= Teacher.Tid 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 Sid,'002',(Select avg(score)
    from SC where Cid='002') from Student where Sid not in (Select Sid from SC where Cid='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 Sid as 学生ID
        ,(SELECT score FROM SC WHERE SC.Sid=t.Sid AND Cid='004') AS 数据库
        ,(SELECT score FROM SC WHERE SC.Sid=t.Sid AND Cid='001') AS 企业管理
        ,(SELECT score FROM SC WHERE SC.Sid=t.Sid AND Cid='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 Sid
    ORDER BY avg(t.score)

18、查询各科成绩{zg}和{zd1}的分：以如下形式显示：课程ID，{zg}分，{zd1}分
    SELECT L.Cid As 课程ID,L.score AS {zg}分,R.score AS {zd1}分
    FROM SC L ,SC AS R
    WHERE L.Cid = R.Cid and
        L.score = (SELECT MAX(IL.score)
                      FROM SC AS IL,Student AS IM
                      WHERE L.Cid = IL.Cid and IM.Sid=IL.Sid
                      GROUP BY IL.Cid)
        AND
        R.Score = (SELECT MIN(IR.score)
                      FROM SC AS IR
                      WHERE R.Cid = IR.Cid
                  GROUP BY IR.Cid
                    );

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.Cid 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.Cid=course.Cid
    GROUP BY t.Cid
    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），xxx（002），OO&UML（003），数据库（004）
    SELECT SUM(CASE WHEN Cid ='001' THEN score ELSE 0 END)/SUM(CASE Cid WHEN '001' THEN 1 ELSE 0 END) AS 企业管理平均分 ,100 * SUM(CASE WHEN Cid = '001' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN Cid ='001' THEN 1 ELSE 0 END) AS 企业管理及格百分数 ,SUM(CASE WHEN Cid = '002' THEN score ELSE 0 END)/SUM(CASE Cid WHEN '002' THEN 1 ELSE 0 END) AS xxx平均分 ,100 * SUM(CASE WHEN Cid = '002' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN Cid ='002' THEN 1 ELSE 0 END) AS xxx及格百分数 ,SUM(CASE WHEN Cid = '003' THEN score ELSE 0 END)/SUM(CASE Cid WHEN '003' THEN 1 ELSE 0END) AS UML平均分 ,100 * SUM(CASE WHEN Cid = '003' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN Cid ='003' THEN 1 ELSE 0 END) AS UML及格百分数
,SUM(CASE WHEN Cid = '004' THEN score ELSE 0 END)/SUM(CASE Cid WHEN '004' THEN 1 ELSE 0END) AS 数据库平均分 ,100 * SUM(CASE WHEN Cid = '004' AND score >= 60 THEN 1 ELSE 0 END)/SUM(CASE WHEN Cid ='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.Tid) AS 教师ID,MAX(Z.Tname) AS 教师姓名,C.Cid 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.Cid=C.Cid and C.Tid=Z.Tid
GROUP BY C.Cid
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），xxx（002），UML （003），数据库（004）
    [学生ID],[学生姓名],企业管理,xxx,UML,数据库,平均成绩
    SELECT DISTINCT top 3
      SC.Sid As 学生学号,
        Student.Sname AS 学生姓名 ,
      T1.score AS 企业管理,
      T2.score AS xxx,
      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.Sid = T1.Sid AND T1.Cid = '001'
            LEFT JOIN SC AS T2
                      ON SC.Sid = T2.Sid AND T2.Cid = '002'
            LEFT JOIN SC AS T3
                      ON SC.Sid = T3.Sid AND T3.Cid = '003'
            LEFT JOIN SC AS T4
                      ON SC.Sid = T4.Sid AND T4.Cid = '004'
      WHERE student.Sid=SC.Sid 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.Sid = T1.Sid AND T1.Cid = 'k1'
            LEFT JOIN sc AS T2
                      ON sc.Sid = T2.Sid AND T2.Cid = 'k2'
            LEFT JOIN sc AS T3
                      ON sc.Sid = T3.Sid AND T3.Cid = 'k3'
            LEFT JOIN sc AS T4
                      ON sc.Sid = T4.Sid AND T4.Cid = '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.Cid 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.Cid=Course.Cid
    GROUP BY SC.Cid,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 Sid,AVG(score) AS 平均成绩
                      FROM SC
                  GROUP BY Sid
                  ) AS T1
            WHERE 平均成绩 > T2.平均成绩) as 名次,
      Sid as 学生学号,平均成绩
    FROM (SELECT Sid,AVG(score) 平均成绩
            FROM SC
        GROUP BY Sid
        ) 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.Sid as 学生ID,t1.Cid as 课程ID,Score as 分数
      FROM SC t1
      WHERE score IN (SELECT TOP 3 score
              FROM SC
              WHERE t1.Cid= Cid
            ORDER BY score DESC
              )
      ORDER BY t1.Cid;

26、查询每门课程被选修的学生数
select cid,count(Sid) from sc group by Cid;

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.Sid,Student.Sname,count(Cid) AS 选课数
from SC ,Student
where SC.Sid=Student.Sid group by SC.Sid ,Student.Sname having count(Cid)=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 Cid,Avg(score) from SC group by Cid order by Avg(score),Cid 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.Sid ,avg(score)
    from Student,SC
    where Student.Sid=SC.Sid group by SC.Sid,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.Sid=Student.Sid and SC.Cid=Course.Cid and Course.Cname='数据库'and score <60;

35、查询所有学生的选课情况；
    SELECT SC.Sid,SC.Cid,Sname,Cname
    FROM SC,Student,Course
    where SC.Sid=Student.Sid and SC.Cid=Course.Cid ;

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.Sid,student.Sname,SC.Cid,SC.score
    FROM student,Sc
    WHERE SC.score>=70 AND SC.Sid=student.Sid;

37、查询不及格的课程，并按课程号从大到小排列
    select cid from sc where scor e <60 order by Cid ;

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.Sid,Student.Sname from SC,Student where SC.Sid=Student.Sid and Score>80 and Cid='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{zg}的学生姓名及其成绩
    select Student.Sname,score
    from Student,SC,Course C,Teacher
    where Student.Sid=SC.Sid and SC.Cid=C.Cid and C.Tid=Teacher.Tid and Teacher.Tname='叶平' and SC.score=(select max(score)from SC where Cid=C.Cid );

41、查询各个课程及相应的选修人数
    select count(*) from sc group by Cid;

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.Sid,B.score from SC A ,SC B where A.Score=B.Score and A.Cid <>B.Cid ;

43、查询每门功成绩{zh0}的前两名
    SELECT t1.Sid as 学生ID,t1.Cid as 课程ID,Score as 分数
      FROM SC t1
      WHERE score IN (SELECT TOP 2 score
              FROM SC
              WHERE t1.Cid= Cid
            ORDER BY score DESC
              )
      ORDER BY t1.Cid;

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 Cid as 课程号,count(*) as 人数
    from sc
    group by Cid
    order by count(*) desc,cid

45、检索至少选修两门课程的学生学号
    select Sid
    from sc
    group by sid
    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 Cid,Cname
    from Course
    where Cid in (select cid from sc group by cid)

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 Sid not in (select Sid from Course,Teacher,SC where Course.Tid=Teacher.Tid and SC.Cid=course.Cid 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 Sid,avg(isnull(score,0)) from SC where Sid in (select Sid from SC where score <60 group by Sid having count(*)>2)group by Sid;

49、检索“004”课程分数小于60，按分数降序排列的同学学号
    select Sid from SC where Cid='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 Sid='001'and Cid='001';

说明：以上sql语句非本站原创，但每一条都经过本站精心整理和严格测试。数据字典仅为参考，请根据实际需要自己完善;在SQL SERVER中均可正常运行，Access中可能会出现错误。转摘请注明出处，谢谢合作！