品种首次供应商写法

select a.*,d.dwmch from fr_spkfk0819 a 

join spkfk b on a.商品编号=b.spbh

left join (select dwbh,spid,row_number() over (PARTITION BY spid order by plh) row from spls_rk) c on b.spid=c.spid and c.row=1

left join mchk d on c.dwbh=d.dwbh