UFN_INSTALLMENT_GETINSTALLMENTWRITEOFFAMOUNT

            create function dbo.UFN_INSTALLMENT_GETINSTALLMENTWRITEOFFAMOUNT(
                @INSTALLMENTID uniqueidentifier
            )
            returns money
            with execute as caller
            as begin
                declare @WRITEOFFAMOUNT money;

                select 
                    @WRITEOFFAMOUNT = sum(coalesce(INSTALLMENTSPLITWRITEOFF.AMOUNT,0))
                from dbo.INSTALLMENT 
                left join dbo.INSTALLMENTSPLIT 
                    on INSTALLMENTSPLIT.INSTALLMENTID = INSTALLMENT.ID
                left join dbo.INSTALLMENTSPLITWRITEOFF 
                    on INSTALLMENTSPLITWRITEOFF.INSTALLMENTSPLITID = INSTALLMENTSPLIT.ID
                where 
                    INSTALLMENT.ID = @INSTALLMENTID;

                return @WRITEOFFAMOUNT;
            end