create table student(
sno varchar2(10) primary key,
sname varchar2(20),
sage number(2),
ssex varchar2(5)
);
create table teacher(
tno varchar2(10) primary key,
tname varchar2(20)
);
create table course(
cno varchar2(10),
cname varchar2(20),
tno varchar2(20),
constraint pk_course primary key (cno,tno)
);
create table sc(
sno varchar2(10),
cno varchar2(10),
score number(4,2),
constraint pk_sc primary key (sno,cno)
);
/*******初始化学生表的数据******/
insert into student values (‘s001‘,‘张三‘,23,‘男‘);
insert into student values (‘s002‘,‘李四‘,23,‘男‘);
insert into student values (‘s003‘,‘吴鹏‘,25,‘男‘);
insert into student values (‘s004‘,‘琴沁‘,20,‘女‘);
insert into student values (‘s005‘,‘王丽‘,20,‘女‘);
insert into student values (‘s006‘,‘李波‘,21,‘男‘);
insert into student values (‘s007‘,‘刘玉‘,21,‘男‘);
insert into student values (‘s008‘,‘萧蓉‘,21,‘女‘);
insert into student values (‘s009‘,‘陈萧晓‘,23,‘女‘);
insert into student values (‘s010‘,‘陈美‘,22,‘女‘);
commit;
/******************初始化教师表***********************/
insert into teacher values (‘t001‘, ‘刘阳‘);
insert into teacher values (‘t002‘, ‘谌燕‘);
insert into teacher values (‘t003‘, ‘胡明星‘);
commit;
/***************初始化课程表****************************/
insert into course values (‘c001‘,‘J2SE‘,‘t002‘);
insert into course values (‘c002‘,‘Java Web‘,‘t002‘);
insert into course values (‘c003‘,‘SSH‘,‘t001‘);
insert into course values (‘c004‘,‘Oracle‘,‘t001‘);
insert into course values (‘c005‘,‘SQL SERVER 2005‘,‘t003‘);
insert into course values (‘c006‘,‘C#‘,‘t003‘);
insert into course values (‘c007‘,‘JavaScript‘,‘t002‘);
insert into course values (‘c008‘,‘DIV+CSS‘,‘t001‘);
insert into course values (‘c009‘,‘PHP‘,‘t003‘);
insert into course values (‘c010‘,‘EJB3.0‘,‘t002‘);
commit;
/***************初始化成绩表***********************/
insert into sc values (‘s001‘,‘c001‘,78.9);
insert into sc values (‘s002‘,‘c001‘,80.9);
insert into sc values (‘s003‘,‘c001‘,81.9);
insert into sc values (‘s004‘,‘c001‘,60.9);
insert into sc values (‘s001‘,‘c002‘,82.9);
insert into sc values (‘s002‘,‘c002‘,72.9);
insert into sc values (‘s003‘,‘c002‘,81.9);
insert into sc values (‘s001‘,‘c003‘,‘59‘);
commit;

练习：
注意：以下练习中的数据是根据初始化到数据库中的数据来写的SQL 语句，请大家务必注意。

select * from student;
select * from teacher;
select * from course;
select * from sc;
1、查询“c001”课程比“c002”课程成绩高的所有学生的学号；
select a.ssno1 from
(select s.sno ssno1,s.score sscore1 from sc s where s.cno=‘c001‘) a left join
(select s.sno ssno2,s.score sscore2 from sc s where s.cno=‘c002‘) b on a.ssno1=b.ssno2
where a.sscore1 > b.sscore2

2、查询平均成绩大于60 分的同学的学号和平均成绩；

select s.sno as 学号,avg(s.score) 平均成绩 from sc s group by s.sno having avg(s.score)>60

3、查询所有同学的学号、姓名、选课数、总成绩；
--方法1
select s.sno,s.sname,count(c.cno),sum(c.score) from student s inner join sc c on s.sno = c.sno group by s.sno,s.sname
--方法2
select s.sno,s.sname,a.countcno,a.sumcscore from student s inner join
(select c.sno csno,count(c.cno) countcno,sum(c.score) sumcscore from sc c group by c.sno) a
on s.sno = a.csno
4、查询姓“刘”的老师的个数；
select count(te.tname) from teacher te where te.tname like ‘刘%‘;
5、查询没学过“谌燕”老师课的同学的学号、姓名；
select stu.sno,stu.sname from student stu where not stu.sname in (
select distinct st.sname from student st left join
(select * from sc s left join
(select * from teacher te inner join course co on te.tno = co.tno) a on s.cno =a.cno) b
on st.sno = b.sno where b.tname =‘谌燕‘
)
6、查询学过“c001”并且也学过编号“c002”课程的同学的学号、姓名；

select st.sno,st.sname from student st join sc ac on st.sno=ac.sno join sc bc on bc.sno=ac.sno
where ac.cno=‘c001‘ and bc.cno=‘c002‘

select st.sno,st.sname from student st inner join
(select a.sno from
(select * from sc s where s.cno=‘c001‘) a inner join
(select * from sc s where s.cno=‘c002‘)
b on a.sno = b.sno) c on st.sno= c.sno
7、查询学过“谌燕”老师所教的所有课的同学的学号、姓名；
select distinct st.sno,st.sname from student st join sc ac on st.sno = ac.sno join course co on ac.cno=co.cno join teacher
te on co.tno=te.tno where te.tname=‘谌燕‘

select distinct st.sno,st.sname from student st left join
(select * from sc s left join
(select * from teacher te inner join course co on te.tno = co.tno) a on s.cno =a.cno) b
on st.sno = b.sno where b.tname =‘谌燕‘
8、查询课程编号“c002”的成绩比课程编号“c001”课程低的所有同学的学号、姓名；

select st.sno,st.sname from student st where st.sno in
(select a.sno from
(select * from sc s1 where s1.cno = ‘c002‘) a,
(select * from sc s2 where s2.cno = ‘c001‘) b where a.sno = b.sno and a.score < b.score)

--9、查询所有课程成绩小于60 分的同学的学号、姓名；
select distinct st.sno,st.sname from student st left join sc ac on st.sno=ac.sno
where ac.score >= 60

select sno,sname from student where sno not in (select sno from sc where score>=60)

--10、查询没有学全所有课的同学的学号、姓名；
select st.sno,st.sname from student st left join sc ac on st.sno = ac.sno
group by st.sno,st.sname having count(ac.cno) < (select count(distinct co.cno) from course co)

select * from student;
select * from teacher;
select * from course;
select * from sc;

11、查询至少有一门课与学号为“s001”的同学所学相同的同学的学号和姓名；
--1
select distinct st.sno,st.sname from student st join sc bc on st.sno=bc.sno where not bc.sno=‘s001‘ and bc.cno in (
select ac.cno from sc ac where ac.sno=‘s001‘)
--2
select su.sno,su.sname from student su where su.sno in (
select sc.sno from sc where sc.cno in (select s.cno from sc s where s.sno=‘s001‘)
and sc.sno<>‘s001‘)
12、查询至少学过学号为“s001”同学所有一门课的其他同学学号和姓名；

select * from sc
left join student st on st.sno=sc.sno where not sc.sno=‘s001‘
and sc.cno in (select cno from sc where sno=‘s001‘)

13、把“SC”表中“谌燕”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(score) from sc where cno in(
select cno from course where tno=( select tno from teacher where tname=‘谌燕‘)))
where cno in(select cno from course where tno=( select tno from teacher where tname=‘谌燕‘));

14、查询和“s001”号的同学学习的课程完全相同的其他同学学号和姓名；
select bc.cno from sc bc where bc.sno <> ‘s001‘ minus
(select sc.cno from sc where sno=‘s001‘)

15、删除学习“谌燕”老师课的SC 表记录；
delete from sc
where cno in (select cno from course
where tno in (select tno from teacher
where tname=‘谌燕‘))

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“c002”课程的同学学号,
“c002”号课的平均成绩；
insert into sc (sno,cno,score)
select distinct st.sno,sc.cno,
(select avg(score)from sc where cno=‘c002‘)
from student st,sc
where not exists
(select * from sc where cno=‘c002‘ and sc.sno=st.sno) and sc.cno=‘c002‘;

17、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 cno ,max(score),min(score) from sc group by cno;
select ac.cno,max(ac.score),min(ac.score) from sc ac group by ac.cno
18、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 cno,avg(score),sum(case when score>=60 then 1 else 0 end)/count(*)
as 及格率
from sc group by cno
order by avg(score) , 及格率 desc
19、查询不同老师所教不同课程平均分从高到低显示

select co.tno,ac.cno,avg(ac.score) from sc ac join course co on ac.cno=co.cno
group by co.tno,ac.cno order by avg(ac.score) desc

select max(t.tno),max(t.tname),max(c.cno),max(c.cname),c.cno,avg(score) from sc , course c,teacher t
where sc.cno=c.cno and c.tno=t.tno
group by c.cno
order by avg(score) desc

20、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.cno,c.cname,
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 c where sc.cno=c.cno group by sc.cno ,c.cname;

21、查询各科成绩前三名的记录:(不考虑成绩并列情况)
select * from
(select s.sno,s.cno,s.score,row_number()over(partition by cno order by s.score desc)
rn from sc s) where rn<4

select * from
(select sno,cno,score,row_number()over(partition by cno order by score desc) rn from sc)
where rn<4

22、查询每门课程被选修的学生数
select s.cno,count(*) from sc s group by s.cno
23、查询出只选修了一门课程的全部学生的学号和姓名
select bc.sno from sc bc join
(select s.cno scno,count(*) a from sc s group by s.cno) scc on bc.cno=scc.scno where a=1
24、查询男生、女生人数
select * from student st
select st.ssex,count(1) from student st group by st.ssex having st.ssex=‘男‘ or st.ssex=‘女‘
25、查询姓“张”的学生名单
select * from student st where st.sname like ‘张%‘
26、查询同名同性学生名单，并统计同名人数
select st.sname,st.ssex,count(1) from student st group by st.sname,st.ssex having count(1)>1
27、1981 年出生的学生名单(注：Student 表中Sage 列的类型是number)

select * from student st where to_char(sysdate,‘yyyy‘)-st.sage=1994
28、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 c.cno,avg(c.score) from sc c group by c.cno order by avg(c.score),c.cno
29、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 * from student st join
(select c.sno c,avg(c.score) from sc c group by c.sno having avg(c.score)>85) aa on st.sno=aa.c
30、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 * from student;
select * from teacher;
select * from course;
select * from sc;
select * from student st join sc ac on st.sno=ac.sno join course co on ac.cno=co.cno
where co.cname=‘Oracle‘ and ac.score<60
31、查询所有学生的选课情况；
select ac.sno,count(1) from student st join sc ac on st.sno=ac.sno group by ac.sno
32、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 st.sname,co.cname,bc.score from student st join sc bc on st.sno=bc.sno join course co on bc.cno=co.cno
where bc.sno in
(select ac.sno from sc ac
where ac.score>70 group by ac.sno) and bc.score>70
33、查询不及格的课程，并按课程号从大到小排列
select ac.cno from sc ac where ac.score<60 group by ac.cno order by ac.cno desc
34、查询课程编号为c001 且课程成绩在80 分以上的学生的学号和姓名；
select * from sc ac where ac.cno=‘c001‘ and ac.score>80
35、求选了课程的学生人数
select count(1) from sc
36、查询选修“谌燕”老师所授课程的学生中，成绩最高的学生姓名及其成绩
select st.sname,c.score from student st join sc c on st.sno=c.sno where c.score in (
select max(c.score) from student st join sc c on st.sno=c.sno join course co
on c.cno=co.cno join teacher te on co.tno=te.tno
where te.tname=‘谌燕‘ )

37、查询各个课程及相应的选修人数
select co.cno,count(co.cno) from sc c left join course co on c.cno=co.cno group by co.cno
38、查询不同课程成绩相同的学生的学号、课程号、学生成绩
select * from sc ac group by ac.cno
39、查询每门功课成绩最好的前两名
select * from
(select ac.sno,ac.score,ac.cno,row_number()over(partition by ac.cno order by ac.score desc)
rn from sc ac) where rn<=2

40、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，若人数相同，按课程号升序排列
select ac.cno,count(ac.sno) from sc ac group by ac.cno having count(ac.sno)>2
order by count(ac.sno) desc,ac.cno

41、检索至少选修两门课程的学生学号
select * from sc
select ac.sno,count(ac.cno) from sc ac group by ac.sno having count(ac.cno)>=2
42、查询全部学生都选修的课程的课程号和课程名
select st.sno,co.cno,co.cname from student st
inner join sc ac on st.sno=ac.sno left join course co on ac.cno=co.cno

43、查询没学过“谌燕”老师讲授的任一门课程的学生姓名

select st.sname from student st join sc ac on st.sno=ac.sno join course co on ac.cno=co.cno join teacher te
on co.tno=te.tno where not te.tname=‘谌燕‘
44、查询两门以上不及格课程的同学的学号及其平均成绩
select bc.sno,avg(bc.score) from sc bc where bc.sno in
(select ac.sno from sc ac where ac.score<60
group by ac.sno having count(ac.score)>2) group by bc.sno

45、检索“c004”课程分数小于60，按分数降序排列的同学学号
select ac.sno from sc ac where ac.cno=‘c004‘ and ac.score<60 order by ac.score desc
46、删除“s002”同学的“c001”课程的成绩
delete sc ac where ac.sno=‘s002‘ and ac.cno=‘c001‘

sql语句总结