UFN_RESERVATION_TOTALVISITORCOUNT

            create function dbo.UFN_RESERVATION_TOTALVISITORCOUNT(@RESERVATIONID uniqueidentifier)
            returns int
            with execute as caller
            as begin
                return isnull((select sum(ITINERARYATTENDEE.QUANTITY)
                                from dbo.ITINERARY
                                inner join dbo.ITINERARYATTENDEE on ITINERARY.ID = ITINERARYATTENDEE.ITINERARYID
                                where ITINERARY.RESERVATIONID = @RESERVATIONID
                            ), 0);
            end