Student(student_id,student_name,student_age,student_sex) 学生表
Course(Course_id,course_name,Teacher_id) 课程表
SC(student_id,Course_id,score) 成绩表
Teacher(Teacher_id,teacher_name) 教师表
答案不知道有没有错，有时间再来修改
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.student_id from
(select student_id,score from SC where Course_id='001') a,
(select student_id,score from SC where Course_id='002') b
where a.score>b.score and a.student_id=b.student_id;
2、查询平均成绩大于60分的同学的学号和平均成绩；
select student_id,avg(score)
from sc
group by student_id having avg(score) >60;
3、查询所有同学的学号、姓名、选课数、总成绩；
select Student.student_id,Student.student_name,count(SC.Course_id),sum(score)
from Student left join SC on Student.student_id=SC.student_id
group by Student.student_id,student_name
4、查询姓“李”的老师的个数；
select count(distinct(teacher_name)) from Teacher where teacher_name like '李%';
5、查询没学过“叶平”老师课的同学的学号、姓名；
select Student.student_id,Student.student_name
from Student
where student_id not in (
select distinct(SC.student_id) from SC,Course,Teacher
where SC.Course_id=Course.Course_id
and Teacher.Teacher_id=Course.Teacher_id
and Teacher.teacher_name='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.student_id,Student.student_name
from Student,SC
where Student.student_id=SC.student_id and SC.Course_id='001'and exists(
Select * from SC as SC_2
where SC_2.student_id=SC.student_id and SC_2.Course_id='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 student_id,student_name
from Student
where student_id in (
select student_id
from SC ,Course ,Teacher
where SC.Course_id=Course.Course_id and Teacher.Teacher_id=Course.Teacher_id and Teacher.teacher_name='叶平' group by student_id having count(SC.Course_id)=(
select count(Course_id) fromCourse,Teacher
where Teacher.Teacher_id=Course.Teacher_id and teacher_name='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 student_id,student_name from
(select Student.student_id,Student.student_name,score ,
(select score from SC SC_2 where SC_2.student_id=Student.student_id and SC_2.Course_id='002') score2
from Student,SC where Student.student_id=SC.student_id and Course_id='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 student_id,student_name
from Student
where student_id not in (
select Student.student_id from Student,SC
where S.student_id=SC.student_id and score>60);
10、查询没有学全所有课的同学的学号、姓名；
select Student.student_id,Student.student_name
from Student,SC
where Student.student_id=SC.student_id
group by Student.student_id,Student.student_name
having count(Course_id) <(select count(Course_id) 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 student_id,student_name
from Student,SC
where Student.student_id=SC.student_id and Course_id in（
select Course_id from SC where student_id='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.student_id,student_name
from Student,SC
where Student.student_id=SC.student_id and Course_id in (
select Course_id from SC where student_id='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.Course_id=SC.Course_id )
from Course,Teacher
where Course.Course_id=SC.Course_id and Course.Teacher_id=Teacher.Teacher_id and Teacher.teacher_name='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 student_id from SC where Course_id in (
select Course_id from SC where student_id='1002')
group by student_id
having count(*)=(select count(*) from SC where student_id='1002');
15、删除学习“叶平”老师课的SC表记录；
Delect SC
from course ,Teacher
where Course.Course_id=SC.Course_id and Course.Teacher_id= Teacher.Teacher_id and teacher_name='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 student_id,'002',(Select avg(score)
from SC where Course_id='002') from Student
where student_id not in (Select student_id from SC where Course_id='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 student_id as 学生ID
,(SELECT score FROM SC WHERE SC.student_id=t.student_id AND Course_id='004') AS 数据库
,(SELECT score FROM SC WHERE SC.student_id=t.student_id AND Course_id='001') AS 企业管理
,(SELECT score FROM SC WHERE SC.student_id=t.student_id AND Course_id='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 student_id
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.Course_id As 课程ID,L.score AS 最高分,R.score AS 最低分
FROM SC L ,SC AS R
WHERE L.Course_id = R.Course_id and
L.score = (SELECT MAX(IL.score)
FROM SC AS IL,Student AS IM
WHERE L.Course_id = IL.Course_id and IM.student_id=IL.student_id
GROUP BY IL.Course_id)
AND
R.Score
= (SELECT MIN(IR.score)
FROM SC AS IR
WHERE R.Course_id = IR.Course_id
GROUP BY IR.Course_id
);
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.Course_id AS 课程号,max(course.course_name)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.Course_id=course.Course_id
GROUP BY t.Course_id
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 Course_id ='001' THEN score ELSE 0 END)/SUM(CASE Course_id WHEN '001' THEN 1 ELSE 0 END) AS 企业管理平均分 ,
100*SUM(CASE WHEN Course_id = '001' AND score >= 60 THEN 1 ELSE 0 END)/SUM( CASE WHEN Course_id = '001' THEN 1 ELSE 0 END) AS 企业管理及格百分数 ,
SUM(CASE WHEN Course_id = '002' THEN score ELSE 0 END)/SUM(CASE Course_id WHEN '002' THEN 1 ELSE 0 END) AS 马克思平均 ,
100*SUM(CASE WHEN Course_id = '002' AND score >= 60 THEN 1 ELSE 0 END)/SUM( CASE WHEN Course_id = '002' THEN 1 ELSE 0 END) AS 马克思及格百分数 ,
SUM( CASE WHEN Course_id = '003' THEN score ELSE 0 END)/SUM(CASE Course_id WHEN '003' THEN 1 ELSE 0 END) AS UML平均分 ,
100*SUM(CASE WHEN Course_id='003' AND score >= 60 THEN 1 ELSE 0 END)/SUM( CASE WHEN Course_id = '003' THEN 1 ELSE 0 END) AS UML及格百分数,
SUM(CASE WHEN Course_id = '004' THEN score ELSE 0 END)/SUM( CASE Course_id WHEN '004' THEN 1 ELSE 0 END) AS 数据库平均分 ,
100*SUM(CASE WHEN Course_id = '004' AND score >= 60 THEN 1 ELSE 0 END)/SUM( CASE WHEN Course_id = '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.Teacher_id) AS 教师ID,MAX(Z.teacher_name) AS 教师姓名,C.Course_id AS 课程ＩＤ,MAX(C.course_name) AS 课程名称,AVG(Score) AS 平均成绩
FROM SC AS T,Course AS C ,Teacher AS Z
where T.Course_id=C.Course_id and C.Teacher_id=Z.Teacher_id
GROUP BY C.Course_id
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.student_id As 学生学号,
Student.student_name 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.student_id = T1.student_id AND T1.Course_id = '001'
LEFT JOIN SC AS T2
ON SC.student_id = T2.student_id AND T2.Course_id = '002'
LEFT JOIN SC AS T3
ON SC.student_id =T3.student_id AND T3.Course_id = '003'
LEFT JOIN SC AS T4
ON SC.student_id = T4.student_id AND T4.Course_id = '004'
WHERE student.student_id=SC.student_id 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.student_id = T1.student_id AND T1.Course_id= 'k1'
LEFT JOIN sc AS T2
ON sc.student_id = T2.student_id AND T2.Course_id = 'k2'
LEFT JOIN sc AS T3
ON sc.student_id = T3.student_id AND T3.Course_id = 'k3'
LEFT JOIN sc AS T4
ON sc.student_id = T4.student_id AND T4.Course_id = '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.Course_id as 课程ID, course_nameas 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.Course_id=Course.Course_id
GROUP BY SC.Course_id,course_name;
24、查询学生平均成绩及其名次
SELECT 1+(SELECT COUNT( distinct 平均成绩)
FROM (SELECT student_id,AVG(score) AS 平均成绩
FROM SC
GROUP BY student_id
) AS T1
WHERE 平均成绩 > T2.平均成绩) as 名次,
student_id as 学生学号,平均成绩
FROM (SELECT student_id,AVG(score) 平均成绩
FROM SC
GROUP BY student_id
) 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.student_id as 学生ID,t1.Course_id as 课程ID,Score as 分数
FROM SC t1
WHERE score IN (SELECT TOP 3 score
FROM SC
WHERE t1.Course_id= Course_id ORDER BY score DESC
)
ORDER BY t1.Course_id;
26、查询每门课程被选修的学生数
select Course_id,count(student_id) from sc group by Course_id;
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.student_id,Student.student_name,count(Course_id) AS 选课数
from SC ,Student
where SC.student_id=Student.student_id group by SC.student_id ,Student.student_name having count(Course_id)=1;
28、查询男生、女生人数
Select count(student_sex) as 男生人数 from Student group by student_sex having student_sex='男';
Select count(student_sex) as 女生人数 from Student group by student_sex having student_sex='女'；
29、查询姓“张”的学生名单
SELECT student_name FROM Student WHERE student_name like '张%';
30、查询同名同性学生名单，并统计同名人数
select student_name,count(*) from Studentgroup by student_name having count(*)>1;;
31、1981年出生的学生名单(注：Student表中student_age列的类型是datetime)
select student_name, CONVERT(char (11),DATEPART(year,student_age)) as age
from student
where CONVERT(char(11),DATEPART(year,student_age))='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 Course_id,Avg(score) from SC group by Course_id order by Avg(score),Course_id 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 student_name,SC.student_id ,avg(score)
from Student,SC
where Student.student_id=SC.student_id group by SC.student_id,student_name 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 student_name,isnull(score,0)
from Student,SC,Course
where SC.student_id=Student.student_id and SC.Course_id=Course.Course_idand Course.course_name='数据库'and score <60;
35、查询所有学生的选课情况；
SELECT SC.student_id,SC.Course_id,student_name,course_name
FROM SC,Student,Course
where SC.student_id=Student.student_id and SC.Course_id=Course.Course_id ;
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.student_id,student.student_name,SC.Course_id,SC.score
FROM student,Sc
WHERE SC.score>=70 AND SC.student_id=student.student_id;
37、查询不及格的课程，并按课程号从大到小排列
select Course_id from sc where scor e <60 order by Course_id ;
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.student_id,Student.student_name from SC,Student where SC.student_id=Student.student_id and Score>80 and Course_id='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.student_name,score
from Student,SC,Course C,Teacher
where Student.student_id=SC.student_id and SC.Course_id=C.Course_id and
C.Teacher_id=Teacher.Teacher_id and Teacher.teacher_name='叶平' and SC.score=(select max(score)from SC where Course_id=C.Course_id );
41、查询各个课程及相应的选修人数
select count(*) from sc group by Course_id;
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.student_id,B.score from SC A ,SC B where A.Score=B.Score and A.Course_id <>B.Course_id ;
43、查询每门功成绩最好的前两名
SELECT t1.student_id as 学生ID,t1.Course_id as 课程ID,Score as 分数
FROM SC t1
WHERE score IN (SELECT TOP 2 score
FROM SC
WHERE t1.Course_id= Course_id
ORDER BY score DESC
)
ORDER BY t1.Course_id;
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 Course_id as 课程号,count(*) as 人数
from sc
group by Course_id
order by count(*) desc,Course_id
45、检索至少选修两门课程的学生学号
select student_id from sc group by student_id 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 Course_id,course_name
from Course
where Course_id in (select Course_id from sc group by Course_id) ;
47、查询没学过“叶平”老师讲授的任一门课程的学生姓名
select student_name from Student where student_id not in (
select student_id
from Course,Teacher,SC
where Course.Teacher_id=Teacher.Teacher_id and SC.Course_id=course.Course_id and teacher_name='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 student_id,avg(isnull(score,0)) from SC where student_id in (
select student_id from SC where
score <60 group by student_id having count(*)>2
)group by student_id;
49、检索“004”课程分数小于60，按分数降序排列的同学学号
select student_id from SC where Course_id='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 student_id='002'and Course_id='001';