Prent-Child relationships in SQL

Hi All,

I have a simple table below and I want to be able to write a SQL select query that returns the grouping_ids until I get no more children. The parent_grouping_id column is the parent to the grouping_id child column. Can somebody please advise me how I can do this in postgreSQL.

CREATE TABLE grouping
(
  grouping_id int4 NOT NULL,
  version int4,
  parent_grouping_id int4,
  topic_topic_id int4,
  CONSTRAINT grouping_pkey PRIMARY KEY (grouping_id),
  CONSTRAINT fk1e2e9d036852722d FOREIGN KEY (topic_topic_id)
      REFERENCES topic (topic_id) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION,
  CONSTRAINT fk1e2e9d03a1bfbfe FOREIGN KEY (topic_topic_id)
      REFERENCES topic (topic_id) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION,
  CONSTRAINT fk1e2e9d03cdaf7222 FOREIGN KEY (parent_grouping_id)
      REFERENCES grouping (grouping_id) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION
)
WITHOUT OIDS;
ALTER TABLE grouping OWNER TO napdba;

Thanks In Advance.