postgresql example function

create or replace function fn_getIsemriDurum(p_durum_id int)
returns varchar
language plpgsql
as $$
declare
   ret_aciklama varchar;
begin
  select aciklama
  into ret_aciklama
  from durumlar
  where id = p_durum_id;
  if not found then
     raise 'Durum id % not found', p_durum_id;
  end if;

  return ret_aciklama;

end;$$