SELECT PID,SaleOrderID,MaterialID,NewOrderNum,OldOrderNum,OldBuyIn  
FROM st_NeedBuyIn AS A
WHERE 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 A
join HtSaleProductDetail AS B on A.MaterialID=B.MaterialID
join (SELECT AlreadySaleProduct FROM HtSaleOrder WHERE PID=24) as C ON B.SaleProductID=C.AlreadySaleProduct