SELECT
(
  CASE
    WHEN HOUR(s.start) BETWEEN 9 AND 14 THEN '09-15'
    WHEN HOUR(s.start) BETWEEN 15 AND 17 THEN '15-18'
    WHEN HOUR(s.start) BETWEEN 18 AND 20 THEN '18-21'
    WHEN HOUR(s.start) BETWEEN 21 AND 23 THEN '21-00'
  END
) PERIOD,
SUM(price),
COUNT(*)
FROM seans s
LEFT JOIN bilet b ON s.id = b.seans_id
GROUP BY
(HOUR(start) BETWEEN 9 AND 14),
(HOUR(start) BETWEEN 15 AND 17),
(HOUR(start) BETWEEN 18 AND 20),
(HOUR(start) BETWEEN 21 AND 23)
ORDER BY period