SELECT t.decTrade_Ext_Price + t.decTrade_Shipping_Charge + t.decTrade_Other_Charge AS NetAmount, (t.decTrade_Product_Balance / t.decTrade_Qty) * NetAmount AS NotShip FROM Trade t JOIN Trading_Partner tp ON tp.iTrading_Partner_ID = t.iTrading_Partner_ID JOIN Product p ON p.sProduct_CD = t.sProduct_CDHowever, this does work with the computation included in the column
SELECT (t.decTrade_Product_Balance / t.decTrade_Qty) * (t.decTrade_Ext_Price + t.decTrade_Shipping_Charge + t.decTrade_Other_Charge) AS NotShip FROM Trade t JOIN Trading_Partner tp ON tp.iTrading_Partner_ID = t.iTrading_Partner_ID JOIN Product p ON p.sProduct_CD = t.sProduct_CD