Optional parameters in Stored Procedure

parameter Declaration
@ShipmentYear INT,
@PartNumber VARCHAR(50),
@SupplierId VARCHAR(50) = NULL,-- Optional parameter with default value NULL
@SerialNumber VARCHAR(50) = NULL,-- Optional parameter with default value NULL
@FromShipmentDate DATE = NULL,-- Optional parameter with default value NULL
@ToShipmentDate DATE = NULL-- Optional parameter with default value NULL

IN where Clause

WHERE
E.ShipmentAddedUser >= 1006 AND
    A.[Year] = @ShipmentYear AND
    C.PartNumber = @PartNumber AND
    (@SupplierId IS NULL OR A.SupplierCode = @SupplierId) AND
    (@SerialNumber IS NULL OR A.SerialNumber = @SerialNumber) AND
    (@FromShipmentDate IS NULL OR @ToShipmentDate IS NULL OR E.ShipmentDate BETWEEN @FromShipmentDate AND @ToShipmentDate);