MySQL / PHP - Trouver des plages horaires disponibles

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;

il vous suffit de fournir des valeurs pour your_duration (entier), start_of_search_window (date et heure) et end_of_search_window (date heure).

Et si vous voulez des cloches et des sifflets...

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;

Vous donnera les trois emplacements disponibles les plus courts (c'est-à-dire les plus proches de la taille cible) dans la fenêtre.