select a.item_id,b.buyer_id from ( select item_id,max(sum(amt)) as max_sum_amt from A where dt>=201807 and dt<=201809 and buyer_id=123 group by 1 )a left join ( select item_id,buyer_id,max(sum(amt)) as max_sum_amt from A where dt>=201807 and dt<=201809 group by 1,2 ) b on a.item_id=b.item_id