SELECT Sales.OID,
               Sales.Number,
               Sales."Date"
FROM Sales,
            Dealer,
            cfgCompany,
            cfgSalesStatus
WHERE Sales.DealerID = Dealer.OID AND
               Sales.CompanyID = cfgCompany.OID AND
               Sales.StatusID = cfgSalesStatus.OID AND
               (Sales.Number =  :SalesNumber OR (0 = :SalesNumber AND
Sales.Number >= 0)) AND
               Dealer.Name LIKE :DealerName AND
              cfgCompany.Description LIKE :CompanyName AND
              cfgSalesStatus.Description LIKE :SalesStatus
ORDER BY Sales.Number DESC

:SalesNumber is an Integer
and the other parameters are Strings

And

SELECT Warranty.OID,
               Warranty.Number,
               SalesLineSerialNumber.SerialNumber
FROM Warranty,
            SalesLineSerialNumber,
            cfgCompany,
            cfgWarrantyStatus
WHERE
               Warranty.CompanyID = cfgCompany.OID AND
               Warranty.StatusID = cfgWarrantyStatus.OID AND
               Warranty.SalesLineSerialNumberID = SalesLineSerialNumber.OID
AND
               (Warranty.Number =  :WarrantyNumber OR (0 = :WarrantyNumber
AND Warranty.Number >= 0)) AND
               SalesLineSerialNumber.SerialNumber LIKE :SerialNumber  AND
              cfgCompany.Description LIKE :CompanyName AND
              cfgWarrantyStatus.Description LIKE :WarrantyStatus
ORDER BY Warranty.Number DESC

:WarrantyNumber is an integer
All other parameters are strings