Simplify Oracle SQL: Treat null date as 'N' and non-null date as 'Y'
I'm not sure what's wrong with your code, but if you don't like all of those 'N''s would 

  select  stricken_chicken_id,
          case when to_char(chicken_hatch_date) is null then
             'N'
          else
             'Y'
          end chicken_hatch_date              
   from   stricken_chicken;


work for you?