$(document).on("click", ".is-default", function() {
         var value = $(this).html();
         var new_value = 'Y';
         var rnum = $(this).attr('rnum');
         var spanID = $(this);

         if (value == 'Y') new_value = 'N';

         var data = "table_name=staff_categories"+
                    "&sequence_flag=N"+
                    "&record_num="+rnum+
                    "&is_default="+new_value;

         $.getJSON("ajax.DataRecord.Update.php", data,
            function(results) {
               $(spanID).html(new_value);
            }
         );
      });