UFN_RESERVATION_GETSECURITYDEPOSITAMOUNTDUE

            CREATE function dbo.UFN_RESERVATION_GETSECURITYDEPOSITAMOUNTDUE
            (
                @ID uniqueidentifier
            ) returns money
            as begin
                return coalesce((select SECURITYDEPOSITAMOUNT from dbo.RESERVATION where ID = @ID), 0)
                        - coalesce((select sum(PAYMENT.AMOUNT)
                                    from dbo.REVENUE as PAYMENT
                                    inner join dbo.RESERVATIONSECURITYDEPOSITPAYMENT on PAYMENT.ID = RESERVATIONSECURITYDEPOSITPAYMENT.PAYMENTID
                                    where RESERVATIONSECURITYDEPOSITPAYMENT.RESERVATIONID = @ID), 0);
            end