行政区划数据下载及整理

从民政部官网（http://www.mca.gov.cn/article/sj/xzqh/2020/）下载数据，导入表area（code,address）

INSERT INTO area_code(`code`,address,province,city,parent_code)
SELECT A.`code`,A.address,B.address AS province,C.address AS city,CASE 
	WHEN C.address IS NULL THEN
		B.`code`
	ELSE
		C.`code`
END
 FROM area A 
LEFT JOIN area B ON CONCAT(SUBSTR(A.`code`,1,2),'0000')=B.`code` AND A.`code`<>B.`code`
LEFT JOIN area C ON CONCAT(SUBSTR(A.`code`,1,4),'00')=C.`code` AND A.`code`<>C.`code`
           

生成行政区划表（code,address,province,city,parent_code）