UFN_REGISTRANT_VALIDCONSTITUENTID

            CREATE function dbo.UFN_REGISTRANT_VALIDCONSTITUENTID
            (
                @EVENTID uniqueidentifier = null,
                @CONSTITUENTID uniqueidentifier = null                
            ) 
            returns bit with execute as caller
            as
            begin                
                if @CONSTITUENTID is not null
                    if (select count(ID) from dbo.REGISTRANT where EVENTID = @EVENTID and CONSTITUENTID = @CONSTITUENTID and ISCANCELLED = 0) > 1
                        return 0

                return 1
            end