LISTING 2: Query to Find subscription_start

SELECT DISTINCT subscriber_name, magazine_name, subscription_start
FROM magazine_subs m
WHERE NOT EXISTS (SELECT * FROM magazine_subs m2
  WHERE 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)