student(Sid,Sname,Sage,Ssex)学生表
Sid：学号
Sname：学生姓名
Sage：学生年龄
Ssex：学生性别
Course(Cid,Cname,T#)课程表
Cid：课程编号
Cname：课程名称
Tid：教师编号
SC(Sid,Cid,score)成绩表
Sid：学号
Cid：课程编号
score：成绩
Teacher(Tid,Tname)教师表
Tid：教师编号：
Tname：教师名字
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 SC a, SC b where a.Sid=b.Sid and a.Cid=001 and b.Cid=002 and a.score>b.score;
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 SC.Sid,Sname,count(Cid),sum(score) from SC,student where SC.Sid=student.Sid group by SC.Sid;
4、查询姓‘李’的老师的个数：
select count(Tname) fromTeacher where tname like '李%';
5、查询没有学过“叶平”老师可的同学的学号、姓名：
select Sid,Sname from student where Sid not in (select Sid from SC where Cid in(select c.Cid from Course c,Teacher t where c.Tid=t.Tid and Tname='李老师' ));
6、查询学过李老师所教的所有课的同学的学号、姓名：
select student.Sid,Sname from student,SC where student.Sid=SC.Sid and Cid in (select Cid from Course ,Teacher where Course.Tid=Teacher.Tid and Tname='李老师') group by SC.Sid having count(Cid)= (select count(Cid) from Course,Teacher where Course.Tid=Teacher.Tid and Tname='李老师') ;
7、查询学过语文并且也学过编号2课程的同学的学号、姓名：
select s.Sid,s.Sname from student s,SC sc1,SC sc2 where s.Sid=sc1.Sid and s.Sid=sc2.Sid and sc1.Cid=2 and sc2.Cid in (select Cid from Course where Cname='语文');
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 student where Sid in (select sc1.Sid from SC sc1,SC sc2 where sc1.Sid=sc2.Sid and sc1.Cid=1 and sc2.Cid=2 and sc1.score>sc2.score);
9、查询所有课程成绩小于60的同学的学号、姓名：
select Sid,Sname from student where Sid not in (select distinct Sid from SC where score>60);
10、查询没有学全所有课的同学的学号、姓名：（where group by having）
select s.Sid,Sname from student s,SC sc where s.Sid=sc.Sid group by s.Sid having count(Cid)<(select count(Cid) from Course);
11、查询至少有一门课与学号为“10”同学所学相同的同学的学号和姓名：
select distinct s.Sid,s.Sname from student s,SC sc where s.Sid=sc.Sid and Cid in (select Cid from SC where Sid=10);
12、查询学过和学号为“10”同学所有课的同学的学号和姓名；
select s.Sid,s.Sname from Student s,SC sc where s.Sid=sc.Sid and Cid in (select Cid from SC where Sid=10) group by s.Sid having count(Cid)=(select count(Cid) from SC where Sid=10);
13、把“SC”表中李老师教的课的成绩都更改为此课程的平均成绩：??
update SC sc set sc.score=(select avg(sc2.score) from SC sc2 ) where sc2.Cid=sc.Cid group by sc2.Cid and Cid in (select c.Cid from Course c,Teacher t where c.Tid=t.Tid and Tname='李老师');
update SC set score = (select avg(sc_2.score) from SC sc_2 where sc_2.cid = sc.cid) where cid in (select c.Cid from course c
left join teacher t on t.Tid = c.Tid where t.Tname = '李老师');
15、删除学习“叶平”老师课的SC表记录：
delete from sc WHERE
cid in (
select c.cid from course c
LEFT JOIN teacher t on c.tid=t.tid
where t.tname = '叶平');
17、按平均成绩从高到低显示所有学生的“语文”、“数学”、“英语”三门的课程成绩，按如下形式显示：学生ID，语文，数学，英语，有效课程数，有效平均分：???
select distinct Sid as 学生id,（select score from SC sc1,Course c where sc1.Cid=c.Cid and sc1.Sid=sc.Sid and Cname='语文') as 语文,(select score from SC sc,Course c where sc.Cid=c.Cid and Cname='数学') as 数学,(select score from SC sc,Course c where sc.Cid=c.Cid and Cname='英语') as英语,count (Cid) as 有效课程数,avg(score) as 有效平均分 from SC sc group by Sid order by avg(score) desc;
18、查询各科成绩最高和最低的分：以如下的形式显示：课程ID，最高分，最低分
select Cid as 课程ID,(select max(score) from SC sc1 where sc1.Cid=sc.Cid ) as 最高分, (select min(score) from SC sc2 where sc2.Cid=sc.Cid) as 最低分 from SC sc group by 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,
c.cname as 课程名,
COALESCE(avg(score),0) as 平均成绩,
100*sum(case
when COALESCE(score,0)>=60
then 1 else 0 END)/count(*) as 及格百分数
from sc t
left join course c
on t.cid = c.cid
group by t.cid
order by 100*sum(case
when COALESCE(score,0)>=60
then 1 else 0 END)/count(*);
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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）：
21、查询不同老师所教不同课程平均分从高到低显示：
select t.tid as 教师id,
t.tname as 教师姓名,
sc.cid as 课程id,
avg(score) as 平均成绩
from sc as sc
LEFT JOIN course c on sc.cid = c.cid
left join teacher t on c.tid = t.tid
group by sc.cid
order by avg(sc.score) desc;
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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)：
23、统计下列各科成绩，各分数段人数：课程ID，课程名称，[100-85],[85-70],[70-60],[ 小于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 '[60-0]'
from sc as sc
left join course as c
on sc.cid = c.cid
group by sc.cid;
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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)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;
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25、查询各科成绩前三名的记录（不考虑成绩并列情况）：
select sid,cid,score
from sc sc_1
where (
select count(3) from sc sc_2
where sc_1.cid = sc_2.cid
and sc_2.score>=sc_1.score)<=2
order by sc_1.cid
);
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26、查询每门课程被选修的学生数：
select cid, count(sid)
from sc
group by cid;
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27、查询出只选修一门课程的全部学生的学号和姓名：
select sc.sid,s.sname,
count(sc.cid) as 课程数
from sc as sc
LEFT JOIN student as s
on sc.sid = s.sid
group by sc.sid
having count(sc.cid)=1;
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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(2) from student
where ssex = '女';
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29、查询姓“张”的学生名单：
select sid,sname
from student
where sname like '张%';
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30、查询同名同姓的学生名单，并统计同名人数：
select sname,count(8)
from student
group by sname
having count(8)>1;
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31、1981年出生的学生名单（注：student表中sage列的类型是datetime）:
32、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 s.sname,sc.sid,avg(sc.score) as 平均成绩
from sc as sc
left join student as s
on sc.sid = s.sid
group by sc.sid
having avg(sc.score)>85;
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33、查询每门课程的平均成绩，结果按平均成绩升序排序，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;
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34、查询课程名称为“数据库”，且分数低于60的学生名字和分数：
select c.cname,s.sid,s.sname,sc.score
from course c
left join sc on sc.cid = c.cid
LEFT JOIN student s on s.sid = sc.sid
where c.cname = '数据库' and sc.score<60;
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35、查询所有学生的选课情况：
select sc.sid,sc.cid,s.sname,c.cname
from sc
LEFT JOIN course c on sc.cid = c.cid
left join student s on sc.sid = s.sid;
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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 s.sid,s.sname,sc.cid,sc.score
from sc
left join student s on sc.sid = s.sid
left join course c on sc.cid = c.cid
where sc.score>70;
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37、查询不及格的课程，并按课程号从大到小的排列：
select cid
from sc
where score<60
ORDER BY cid;
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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,s.sname
from sc
left join student s on sc.sid = s.sid
where sc.cid = '003' and sc.score>80;
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39、求选了课程的学生人数：
select count(2) from
(select distinct sid from sc)a;
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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 s.sname,sc.score
from sc sc
left join student s on sc.sid = s.sid
left join course c on sc.cid = c.cid
left join teacher t on c.tid = t.tid
where t.tname = '叶平'
and sc.score = (
select max(score)
from sc sc_1
where sc.cid = sc_1.cid);
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41、查询各个课程及相应的选修人数：
select cid,count(*) from sc group by cid;
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42、查询不同课程成绩相同的学生和学号、课程号、学生成绩：
select DISTINCT a.sid,a.cid,a.score
from sc as a ,sc as b
where a.score = b.score
and a.cid <> b.cid;
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43、查询每门课程成绩最好的前两名：
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序，若人数相同，按课程号升序排序：
select cid as 课程号,count(8) as 选修人数
from sc
group by cid
HAVING count(sid)>10
order by count(8) desc,cid;
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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(8)>=2;
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46、查询全部学生选修的课程和课程号和课程名：
select cid,cname
from course
where cid in (select cid from sc group by cid);
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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 sc,course,teacher
where course.tid = teacher.tid and sc.cid = course.cid
and teacher.tname='叶平'
);
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48、查询两门以上不及格课程的同学的学号以及其平均成绩：
select sid,avg(COALESCE(score,0))
from sc
where sid in (
select sid
from sc
where score<60
group by sid
having count(8)>2
)
group by sid;
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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,score
from sc
where cid='004'
and score<60
order by score desc;
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50、删除“002”同学的“001”课程的成绩：
delete from sc
where sid = '002'
and cid = '001';
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版权声明：本文为CSDN博主「我家有只小熊二」的原创文章，遵循CC 4.0 BY-SA版权协议，转载请附上原文出处链接及本声明。
原文链接：https://blog.csdn.net/hundan_520520/article/details/54881208