2017省市区镇街道)级联sql

CREATE TABLE `c_region_level_4` ( `id` smallint(5) unsigned NOT NULL AUTO_INCREMENT, `code` int(10) unsigned DEFAULT NULL, `parent_id` mediumint(8) unsigned DEFAULT NULL, `name` varchar(50) DEFAULT NULL, `level` tinyint(1) unsigned DEFAULT NULL, PRIMARY KEY (`id`), KEY `parent_id` (`pa