让查询语句中出现你想要的值

1 将某一字段查询结果变为NULL

select br_id, br_name, br_shorttitle, null as br_uppid, br_flag, br_remark 

from base_region where br_id='420100' 

union 

select br_id, br_name, br_shorttitle, br_uppid, br_flag, br_remark 

from base_region where br_uppid='420100'