Jeśli Null to wpisz zawartość kolumny X

 SELECT        it__Item.it_ExternalItemId AS [ID Subiekt], 
			it__Item.it_Name AS Nazwa, 
			it__Item.it_Symbol AS Symbol, 
			au__Auction.au_Title AS [Tytul aukcji], 
			au__Auction.au_Number AS Numer, 
			sl_CustomAttributes.cat_Name, 
                         it_CustomAttributes.ia_AttributeValue AS [ID Wlasne], 
			sl_CustomAttributes.cat_Id
FROM            sl_CustomAttributes INNER JOIN
                         it_CustomAttributes ON sl_CustomAttributes.cat_Id = it_CustomAttributes.ia_AttributeId FULL OUTER JOIN
                         au__Auction INNER JOIN
                         it__Item ON au__Auction.au_ProductId = it__Item.it_Id ON it_CustomAttributes.ia_ItemId = it__Item.it_Id
WHERE        (au__Auction.au_State = 3) AND ((sl_CustomAttributes.cat_Id = 1000) OR
                         (sl_CustomAttributes.cat_Id IS NULL))
ORDER BY Nazwa