代码：

create database if not exists test default charset utf8 collate utf8_general_ci; use test; drop table if exists area; create table area ( aid int unsigned primary key auto_increment, atitle varchar(255), pid int );

insert into area values ('130000', '河北省', NULL), ('130100', '石家庄市', '130000'), ('130400', '邯郸市', '130000'), ('130600', '保定市', '130000'), ('130700', '张家口市', '130000'), ('130800', '承德市', '130000'), ('440000', '广东省', NULL), ('440300', '深圳市', '440000'), ('440100', '广州市', '440000'), ('440500', '汕头市', '440000'), ('440600', '佛山市', '440000'), ('440200', '韶关市', '440000'), ('130101', '石家庄一区', '130100'), ('440101', '广州越秀区', '440100');

查询河北省的市 查询河北省的市和区