WITH w AS (
SELECT person_id
FROM person
WHERE per_db = 'Y')
SELECT per_h_email
FROM person p, w
WHERE p.person_id = w.person_id
AND p.per_ok2_email = 'A'
AND p.per_h_email IS NOT NULL
UNION
SELECT po_w_email
FROM poie o, w
WHERE o.person_id = w.person_id
AND o.po_status = 'A'
AND o.po_w_email IS NOT NULL;