>I have a stored procedure called ap_LookupPart. It must be provided a warehouse Id and a part no. The Serial number is optional. If
>I don't pass a serialno, no data is returned. I don't understand why this isn't working:
>
>

>CREATE PROCEDURE ap_LookupPart
>	@WarehouseId	INT,
>	@PartNo			VARCHAR(30),
>	@SerialNo		VARCHAR(30) = NULL
>	
>AS
>BEGIN
>
>	SELECT i.*, p.PartNo, p.Description, l.Location, w.WarehouseCode, w.Caption AS Warehouse
>		FROM Inventory i
>		JOIN Parts p ON p.PartId = i.PartId
>		JOIN Locations l ON l.LocationId = i.LocationId
>		JOIN Warehouses w ON w.WarehouseId = i.WarehouseId
>		WHERE w.WarehouseId = @WarehouseId AND
>			  p.PartNo = @PartNo AND
>			  i.SerialNo = ISNULL(@SerialNo, i.SerialNo)
>
>END
>

Kevin,

Do you have NULLs in the SerialNo column?

Try AND (@SerialNo IS NULL OR i.SerailNo = @SerialNo) instead of iSerialNo = ISNULL(@SerialNo, i.SerialNo)