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
问题:
select a.sid from
(select sid,score from sc where cid='001')a,
(select sid,score from sc where cid='002')b
where a.sid = b.sid and a.score>b.score;
select sid,avg(score) from sc
group by sid
having avg(score)>60;
select s.sid,s.sname,count_cid as 选课数,
sum_score as 总成绩
from student s
left join
(select sid,count(cid) as count_cid,sum(score) as sum_score
from sc group by sid )sc
on s.sid = sc.sid;
select count(tname)
from teacher
where tname like '李%';
select s.sid,s.sname
from student as s
where s.sid not in (
select DISTINCT sid
from sc as sc
where sc.cid in (
select cid
from course as c
left join teacher as t on c.tid = t.tid
where t.tname = '叶平')
);
select s.sid,s.sname
from student as s
where s.sid in (
select distinct sc.sid
from sc as sc
where sc.cid in (
select cid
from course as c
left join teacher as t on c.tid = t.tid
where t.tname = '叶平')
group by sc.sid
HAVING count(cid)=
(select count(cid)
from course as c left join teacher as t on c.tid = t.tid
where t.tname = '叶平')
);
SELECT s.sid,s.sname
from student as s
left join sc as sc on s.sid = sc.sid
where sc.cid = '001'
and EXISTS(
select * from sc as sc_2
where sc.sid = sc_2.sid
and sc_2.cid='002');
select s.sid,s.sname
from student as s
left join sc as sc
on sc.sid = s.sid
where sc.cid = '001'
and s.sid in (
select sid from sc as sc_2
where sc_2.cid='002'
and sc_2.sid = sc.sid);
select sid,sname
from (select student.sid,student.sname,score,
(select score from sc as sc_2
where sc_2.sid = student.sid
and sc_2.cid = '002') as score2
from student,sc
where student.sid=sc.sid and cid = '001') s_2
where score2<score;
select sid,sname
from student
where sid not in
(select s.sid
from student s,sc
where s.sid=sc.sid and score>60 );
select sid,sname
from student s
where not EXISTS (
select s.sid from sc
where sc.sid = s.sid and sc.score>60);
select s.sid,s.sname
from student s ,sc sc
where s.sid = sc.sid
group by s.sid,s.sname
having count(sc.cid)<(
select count(cid)
from course);
select s.sid,s.sname
from student s
right join sc sc on s.sid = sc.sid
group by s.sid,s.sname
having count(sc.cid)<
(select count(cid) from course);
select student.sid,sname
from student,sc
where student.sid = sc.sid
and cid in
(select cid from sc where sid='1001');
select s.sid,s.sname
from sc sc left join student as s
on sc.sid = s.sid
where sc.cid in (select cid from sc where sid='1001');
select sc_1.sid,s.sname
from sc sc_1 left join student as s
on sc_1.sid = s.sid
where
exists (select sc_2.cid from sc as sc_2
where sc_1.cid = sc_2.cid
and sc_2.sid = '1001');
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 = '叶平');
select sc_1.sid
from (select cid from sc where sid='1002')a
left join sc sc_1 on a.cid = sc_1.cid
where sc_1.sid<>'1002'
group by sc_1.sid
having count(sc_1.cid) =
(select count(cid) from sc where sid='1002');
select a.sid,s.sname from
(select sid,GROUP_CONCAT(cid order by cid separator ',') as cid_str
from sc where sid='1002')b,
(select sid,GROUP_CONCAT(cid order by cid separator ',') as cid_str
from sc group by sid)a
left join student s
on a.sid = s.sid
where a.cid_str = b.cid_str and a.sid<>'1002';
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');
insert into sc select sid,'002',
(select avg(score) from sc where cid='0022')
from student
where sid not in (select sid from sc where cid='002');
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='015') as 英语,
count(cid) 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);
select l.cid as 课程id,l.score as 最高分,
r.score as 最低分
from sc l,sc r
where l.cid = r.cid
and l.score =
(select max(t.score) from sc t
where l.cid = t.cid group by t.cid)
and r.score = (select min(t.score) from sc t
where r.cid = t.cid group by t.cid)
order by l.cid;
select cid as 课程id,max(score) as 最高分,
min(score) as 最低分
from sc
group by cid;
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(*);
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;
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;
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;
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
);
select cid, count(sid)
from sc
group by cid;
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;
select count(ssex) as 男生人数
from student
group by ssex
having ssex = '男';
select count(2) from student
where ssex = '女';
select sid,sname
from student
where sname like '张%';
select sname,count(8)
from student
group by sname
having count(8)>1;
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;
select cid,avg(score)
from sc
group by cid
order by avg(score),cid desc;
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;
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;
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;
select cid
from sc
where score<60
ORDER BY cid;
select sc.sid,s.sname
from sc
left join student s on sc.sid = s.sid
where sc.cid = '003' and sc.score>80;
select count(2) from
(select distinct sid from sc)a;
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);
select cid,count(*) from sc group by cid;
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;
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;
select sid
from sc
group by sid
having count(8)>=2;
select cid,cname
from course
where cid in (select cid from sc group by cid);
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'
);
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;
select sid,score
from sc
where cid='004'
and score<60
order by score desc;
delete from sc
where sid = '002'
and cid = '001';
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