function addparameter
  (p_event_id    in athoa.event_values.event_id%type,
   p_event_value in athoa.event_values.event_value%type)
  return athoa.event_parameters.parameter_order%type
is
  pragma autonomous_transaction;
 
  v_parameter_order     athoa.event_parameters.parameter_order%type;
  v_event_parameter_id  athoa.event_parameters.event_parameter_id%type;
begin
  if p_event_id is null then
    raise_application_error(-20000, 'p_event_id is null');
  elsif p_event_value is null then
    raise_application_error(-20000, 'p_event_value is null');
  end if;
 
  select event_parameter_id, parameter_order
    into v_event_parameter_id, v_parameter_order
    from athoa.event_parameters
   where log_id = (select log_id
                     from athoa.event_events
                    where event_id = p_event_id)
     and parameter_order = (select count(*) + 1
                              from athoa.event_values
                             where event_id = p_event_id);
   
  insert into athoa.event_values
    (
    event_id,
    event_parameter_id,
    event_value
    )
    values
    (
    p_event_id,
    v_event_parameter_id,
    p_event_value
    );
 
  commit;
 
  return (v_parameter_order);
end;