MySQL / PHP - Намерете налични времеви слотове

SELECT a.end AS free_after
FROM bookings a
WHERE NOT EXISTS (
  SELECT 1
  FROM bookings b
  WHERE b.start BETWEEN a.end AND a.end + INTERVAL your_duration HOURS
)
AND a.end BETWEEN start_of_search_window AND end_of_search_window;

просто трябва да предоставите стойности за your_duration (цяло число), start_of_search_window (дата, час) и end_of_search_window (дата и час).

И ако искате звънци и свирки....

SELECT free_from, free_until
FROM (
  SELECT a.end AS free_from,
  (SELECT MIN(c.start)
   FROM bookings c
   WHERE c.start > a.end) as free_until
  FROM bookings a
  WHERE NOT EXISTS (
    SELECT 1
    FROM bookings b
    WHERE b.start BETWEEN a.end AND a.end + INTERVAL your_duration HOUR
  )
  AND a.end BETWEEN start_of_search_window AND end_of_search_window
)
ORDER BY free_until-free_from
LIMIT 0,3;

Ще ви даде трите най-къси налични слота (т.е. най-близкият до целевия размер) в рамките на прозореца.