跨表指定数据更新

select bh.*,h4.* from bh,h4 where bh.aspdm=h4.h4spdm and bh.ajiage!=h4.h4jiage

update bh set ajiage=(select h4jiage from h4 where h4spdm=bh.aspdm) where aspdm in (SELECT h4spdm FROM h4)