Student(Sid,Sname,Sage,Ssex) 学生表
Course(Cid,Cname,Tid) 课程表
SC(Sid,Cid,score) 成绩表
Teacher(Tid,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.Sid from (select Sid,score from SC where Cid='001') a 
(select Sid,score from SC where Cid='002') 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完全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.Cid As 课程ID,L.score AS 最高分,R.score AS 最低分
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），马克思（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 马克思平均分
,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 马克思及格百分数
,SUM(CASE WHEN Cid = ‘003’ THEN score ELSE 0 END)/SUM(CASE Cid WHEN ‘003’ THEN 1 ELSE 0 END) 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 0 END) 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），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.Sid 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.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，成绩最高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、查询每门功成绩最好的前两名
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