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893天前create table class( |
classno number(2)primary key, |
cname varchar(10) not null |
); |
create table student( |
stuno number(8) primary key,--主键 |
sname varchar2(12) not null, |
sex char(4) default '女',--默认 |
birthday char(8), |
email varchar2(20) unique,--唯一 |
score number(5,2), |
classno number(2) references class(classno) |
); |
drop table student; |
insert into class |
select 1,'一班' from dual union |
select 2,'二班' from dual union |
select 3,'三班' from dual; |
|
insert into student values |
(21,'tom','男','19790203','tom@163.net',89.50,1); |
insert into student values |
(56,'jerry',default,null,null,0,2); |
insert into student values |
(33,'wenney','男','19890203','wenney@189.net',null,3); |
SELECT * FROM student; |
delete from student; |
--将student表中所有一班学生的成绩加10分 |
update student set score=score+10 |
where classno=(select classno from class where cname='一班'); |
--删除student表中所有3班出生日期晚于1988年5月12日的学生 |
delete student where to_date(birthday,'yyyymmdd')>to_date |
('19880512','yyyymmdd') and classno=(select classno from class |
where cname='三班' |
); |
--按班级升序 成绩降序排序 |
select * from student order by classno,score desc; |
--查询三班成绩为空的学生 |
select * from student where classno=(select classno |
from class where cname='三班') and score is null; |
--查询所有学生的学号，姓名，成绩，班级名称 |
select s.stuno,s.sname,s.score,d.cname from student s join |
class d on s.classno=d.classno; |
--按班级统计每个班的人数，最高分，最低分，平均分，按平均分降序排序 |
select count(*) "人数",max(score) "最高分",min(score) "最低分", |
avg(nvl(score,0)) "平均分" from student group by classno |
order by avg(nvl(score,0)) desc; |
by: 发表于：2017-09-28 14:48:25 顶(0) | 踩(0) 回复
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