oracle基础命令、sql语句、建表、自增、分页查询、联查
建表
create table stu(
uid number(5) primary key,
uname varchar2(50) not null
)
table banji(
bjid number(5),
bjname varchar2(50) not null
constraint pk_bjid primary key (bjid)
)
create table stu(
userid number(5),
username varchar2(50) not null,
phone varchar2(11),
sex varchar2(5),
bjid number(5),
constraint pk_userid primary key (userid),
constraint uq_username unique (phone),
constraint ck_sex check(sex in ('男','女')),
constraint fk_banji_stu foreign key (bjid) references banji(bjid) ON DELETE SET NULL
)
自增
- 创建一个序列sequence
create sequence stu_id_seq; - 使用stu_id_seq.nextval获取下一个值。
insert into stu values(stu_id_seq.nextval,‘andy5’,‘13012341239’,‘男’,1);
insert into stu values(stu_id_seq.nextval,‘andy6’,‘13012341285’,‘男’,2);
insert into stu values(stu_id_seq.nextval,‘andy7’,‘13012341256’,‘男’,3);
分页查询
伪类ROWNUM可以给原结果集前,加一个列标记列,从1开始。
select t.*
from (
select rownum r,g.* from grouptable_ms g
) t
where t.r >=1 and t.r<=5
联查
左外联接,已班级表为主
select s.*,b.*
from banji b
left join stu s
on b.bjid = s.bjid
等效的写法,把(+)写在副表的字段后面。
select s.*,b.*
from banji b,stu s
where b.bjid = s.bjid(+)
字段类型、约束、展示用户名、执行sql脚本、导出导入、变量标记、外键约束
字段类型、约束、展示用户名、执行sql脚本、导出导入、变量标记、外键约束:https://blog.csdn.net/weixin_43583693/article/details/90270940