1 WITH SUBQUERY AS (

 2     SELECT
 3         ORGID
 4     FROM
 5         OM_ORGANIZATION
 6     WHERE
 7         PARENTORGID = 'ROOT'


 8     UNION ALL


 9         SELECT
10             B.ORGID
11         FROM
12             SUBQUERY A,
13             OM_ORGANIZATION B
14         WHERE
15             B.PARENTORGID = A.ORGID

16 ) SELECT DISTINCT
17     *
18 FROM
19     SUBQUERY

​