LISTING 6: Revised Query That Uses OUTER JOIN
 to Find subscription_start

SELECT DISTINCT m.subscriber_name, m.magazine_name, m.subscription_start
FROM magazine_subs m LEFT OUTER JOIN magazine_subs m2
  ON m2.subscriber_name = m.subscriber_name
  AND m2.magazine_name = m.magazine_name
  AND m2.subscription_start < m.subscription_start
  AND m2.subscription_end >= m.subscription_start
WHERE m2.subscriber_name IS NULL