Query returning exact number of rows

Question

I have a table that stores two foreign keys, implementing a n:m relationship.

One of them points to a person (subject), the other one to a specific item.

Answer 1

I was able to come up to this simplistic solution: First returning all the values i may select then looping returning null values while we have the right amount. Posting it here if someone would stumble on the same problem. Still looking for easier/faster solutions if they exist.

CREATE OR REPLACE FUNCTION fnk_abonemento_nariai(prm_item integer)
  RETURNS SETOF subject_items AS
$BODY$DECLARE _kiek integer;
DECLARE _rec subject_items;
DECLARE _counter integer;
BEGIN
  /*get the number of records we need*/
  SELECT INTO _kiek num_records
  FROM subjekto_abonementai
    WHERE num_id = prm_item;

  /*get the records that actualy exist */

  FOR _rec IN SELECT sub_item, sal_subject
      FROM sal_subject 
      WHERE sub_item = prm_item LOOP
    return 
      next _rec;
    _counter := COALESCE(_counter, 0) + 1;
  END LOOP;

  /*fill the rest with null values*/

  While _kiek > _counter loop
    _rec.sub_item := NULL;
    _rec.sal_subject := NULL;
    Return next _rec;
    _counter := COALESCE(_counter, 0) + 1;
  end loop;

END;$BODY$
  LANGUAGE plpgsql VOLATILE;