Select a. * , isnull (b.实收数量, 0 ) as 实收数量 from A1 a left join ( select 物料编码, sum (实收数量) as 实收数量 from A2 group by 物料编码 ) b on a.物料编码 = b.物料编码 where a.采购订单 = ' 001 '