reversion? Recursion question

Hello,
For lack of a better title, I need to a reverse recursion.  Where I have
the parent ID, but then I need to find all it's children, grandchildren,
great-grandchildern, etc for the parent-id.  I guess this would be like a
directory and all its sub-directories.

I modified a normal recursive function I got from the cookbook , but it's
impossible for me to decipher where the top level begins and the children
end.
Could someone point me in the right direction to clean this up?  I can
provide sample data if needed.

TIA
Patrick Hatcher




-Table
CREATE TABLE mdc_category ( keyp_category int4 NOT NULL, category_name varchar(255),  parent_keypcategoryid int4,
CONSTRAINTxpkmdc_category UNIQUE (keyp_category)
 
)


CREATE FUNCTION category_descriptiontest(int4) RETURNS varchar AS '
DECLARE v_category_id ALIAS FOR $1;
DECLARE tmp_record RECORD;
DECLARE tmp_id VARCHAR;
DECLARE tmp_code VARCHAR;
DECLARE keycheck  INT4;
BEGIN
tmp_code:='''';
FOR tmp_record IN SELECT keyp_category,category_name,parent_keypcategoryid
from  mdc_category  where parent_keypcategoryid = v_category_id LOOP
IF tmp_record.parent_keypcategoryid=0 THEN   RETURN tmp_record.keyp_category; END IF;
tmp_id:=category_descriptiontest(tmp_record.keyp_category); IF tmp_record.keyp_category<>0  THEN     tmp_code:=
tmp_code|| ''
 
-'' ||   tmp_id::varchar  || tmp_record.keyp_category::varchar || '' -'';

/*     tmp_code:= tmp_code || '''' || tmp_id::varchar || ''
-'' || tmp_record.keyp_category::varchar;
*/  END IF;

END LOOP;

RETURN tmp_code;END; '  LANGUAGE 'plpgsql';