时间：2021-07-01 10:21:17 帮助过：52人阅读
SELECT userinfo.id, user_name, role, adm_regionid, region_name , create_timeFROM userinfoLEFT JOIN region ON userinfo.adm_regionid = region.id结果：
设置显示默认值：
SELECT userinfo.id, user_name, role, adm_regionid, IFNULL(region_name,0) as region_name, create_timeFROM userinfoLEFT JOIN region ON userinfo.adm_regionid = region.id即：如果region_name一列的值为空，则显示为0，结果为：
