Question about formula column

Question

Trying to use formula column with an nvl. The problem is that if the record is not there the nvl will not work. How do I force the formula column to return something when the record is not there. Below is the formula.
function CF_1FORMULA0028 return Char is
myComments varchar(50);
begin
select nvl(erActRelData.VALUE,'') into myComments
          from      dpss_gdats.er_activity eractivity,
                              dpss_gdats.er_activity_relevant_data erActRelData,
                              dpss_gdats.er_activity_rel_data_name erActRelDataName
               where eractivity.er_case_id = :case_number
               and eractivity.date_created is not null
               and eractivity.ER_ACTIVITY_ID = erActRelData.ER_ACTIVITY_ID
               and erActRelData.ER_ACTIVITY_REL_DATA_NAME_ID = erActRelDataName.ER_ACTIVITY_REL_DATA_NAME_ID
               and erActRelDataName.NAME = 'Comments';     
                    return myComments;
end;

Answer 1

Modify the last statement to
return nvl(myComments,'Null Value');