我一直在做客户项目。我需要从购买的产品QTY和出售的QTY中获得库存。SELECT DISTINCTROW tbl_itemmaster.product_code,tbl_itemmaster.unittype,tbl_itemmaster.color,SUM(tbl_purchasedetails.qty),SUM(tbl_saledetails.qty),(SUM(tbl_purchasedetails.qty)-SUM(tbl_saledetails.qty))
FROM (tbl_itemmaster LEFT JOIN tbl_saledetails ON tb