CREATE TABLE "zzz"."table" (
  "id" SERIAL, 
  "parent_id" INTEGER, 
  "position" SMALLINT DEFAULT  0 , 
  "name" VARCHAR( 256 ), 
  CONSTRAINT "zzz_pkey" PRIMARY KEY("id"), 
  CONSTRAINT "zzz_fk_parent" FOREIGN KEY ("zzz_id")
    REFERENCES "zzz"."table"("id")
    ON DELETE CASCADE
    ON UPDATE NO ACTION
    NOT DEFERRABLE
) WITH OIDS;

BEGIN
    UPDATE
        zzz.table
    SET
        position = position - 1 
	WHERE
        position > OLD.position;
    RETURN NULL;
END;

    ON DELETE SET NULL
    ON UPDATE NO ACTION

DECLARE
    row record;
BEGIN
    UPDATE
        zzz.table
    SET
        position = position - 1 
	WHERE
        position > OLD.position;

    FOR row IN
        SELECT table.id
        FROM zzz.table
        WHERE table.parent_id = OLD.id
    LOOP
        DELETE FROM zzz.table
        WHERE table.id = row.id;
    END LOOP;
    RETURN OLD;
END;