>And if the item never was purchased - latest from the stock? What if you update your stock from other source (e.g. item in stock has later date when purchased item)?
>
>
>Then Openinge rate will be use

Try:

SELECT O.Codes as [Code], O.Products, ;
OpeningQty as [OpeningQty], ;
PurchaseQty as [PurchaseQty], ;
PurchaseAmount as [PurchaseAmount], ;
OpeningQty + NVL(PurchaseQty,0) as [TotalQty], ;
OpeningAmount + NVL(PurchaseAmount,0) as [TotalAmount], ;
NVL(SoldQty,0) as [SoldQty], ;
NVL(SoldAmount,0) as [SoldAmount], ;
OpeningQty + NVL(PurchaseQty,0) - NVL(SoldQty,0) as [ClosingQty], ;
(OpeningQty + NVL(PurchaseQty,0) - NVL(SoldQty,0)) * IIF(LastStocked > NVL(LastPurchased,{}),LastStockRate, LastPurchaseRate) as [ClosingAmount] ;
 FROM (select Codes, Products, SUM(qty) as OpeningQty, ;
SUM(Amount) as OpeningAmount, MAX(dates) as LastStocked from Open_Stock group by Codes, Products) O ;
INNER JOIN (select Rate as LastStockRate, Codes, Dates FROM Open_Stock) O1 ON O.Codes = O1.Codes AND O.LastStocked = O1.Dates ;
LEFT JOIN (select Codes, Products, ;
SUM(qty) as PurchaseQty, SUM(Amount)  as PurchaseAmount, MAX(Dates) as LastPurchased ;
from Purchase group by Codes, Products) P ;
ON O.Codes = P.Codes ;
LEFT JOIN (select Rate as LastPurchaseRate, Codes, Dates FROM Purchase) P1 on P.Codes = P1.Codes and P.LastPurchased = P1.Dates ;
LEFT JOIN (select Codes, Products, ;
SUM(qty) as SoldQty, SUM(Amount) as SoldAmount ;
from Sales group by Codes, Products) S ;
ON O.Codes = S.Codes