把子查询所得到的列作为运算列
SELECT PID,SaleOrderID,MaterialID,NewOrderNum,OldOrderNum,OldBuyIn FROM st_NeedBuyIn AS AWHERE EXISTS( SELECT MaterialID,Number FROM HtSaleProductDetail AS B WHERE SaleProductID=( SELECT AlreadySaleProduct FROM HtSaleOrder WHERE PID=24 ) AND A.MaterialID=B.MaterialID)
SELECT PID,SaleOrderID,MaterialID,NewOrderNum,OldOrderNum,(OldBuyIn*B.Number) OldBuyIn FROM st_NeedBuyIn AS Ajoin HtSaleProductDetail AS B on A.MaterialID=B.MaterialIDjoin (SELECT AlreadySaleProduct FROM HtSaleOrder WHERE PID=24) as C ON B.SaleProductID=C.AlreadySaleProduct