自关联
create table areas(
id INT NOT NULL PRIMARY KEY AUTO_INCREMENT,
name varchar(50) NOT NULL,
parent_id int,
constraint parent foreign key(parent_id) references areas(id)
)ENGINE=InnoDB DEFAULT CHARSET=utf8;
导入数据
source areas.sql;查询黑龙江下的所有市
select c.* from areas as c
inner join areas as p on c.parent_id=p.id
where p.name='黑龙江省';
查询广州市下的区县
select dis.*,dis1.* from areas as dis
inner join areas as city on city.id = dis.parent_id
left join areas as dis1 on dis.id=dis1.parent_id
where city.name='广州市';
