CREATE TABLE ATable (ID INTEGER, ParentID INTEGER)

INSERT INTO ATable 
SELECT 1, NULL
UNION ALL SELECT 2, 1
UNION ALL SELECT 3, 2

;WITH q AS (
  SELECT  ID, ParentID
  FROM    ATable
  UNION ALL 
  SELECT  a.ID, a.ParentID
  FROM    ATable a
          INNER JOIN q ON q.ID = a.ParentID
)
SELECT  DISTINCT *
FROM    q