贡献一份世界范围的省市区三级联动下拉选择mysql数据库，当时花了很久的精力才整合到的；希望对有需要的人有一点帮助。亲测非常好用，欢迎大家下载研究！(It took a long time to integrate a worldwide MySQL database into cities and towns, hoping to help people in need. Pro test is very good, welcome to download research!)