event.sql

SELECT
  e.id AS event_id,
  e.name,
  s1.id AS schedule_id,
  date_format(s1.due_date, '%Y/%m/%d') AS due_date
FROM events e
LEFT JOIN schedules s1
  ON e.id = s1.event_id
WHERE s1.id IS NULL
  OR s1.id = (
    SELECT s2.id
    FROM schedules s2
    WHERE s2.event_id = e.id
      AND s2.due_date >= (SELECT max(sysdate) FROM sysdate_dummy)
    ORDER BY
      s2.due_date
    LIMIT 1
  )
ORDER BY
  s1.id IS NULL,
  s1.due_date,
  e.id