UFN_EVENTSEATINGSEAT_UNIQUEREGISTRANTID

            create function dbo.UFN_EVENTSEATINGSEAT_UNIQUEREGISTRANTID
            (
                @REGISTRANTID uniqueidentifier = null                
            ) 
            returns bit with execute as caller
            as
            begin            
                if @REGISTRANTID is not null begin
                        if (select count(ID) from dbo.EVENTSEATINGSEAT where REGISTRANTID = @REGISTRANTID) = 1
                            return 1;
                        else
                            return 0;
                end

                return 1;
            end