SELECT
    DISTINCT EXTRACT(week FROM arrival_time ::date) AS week_number,
    COUNT( ticket_flights.ticket_no) AS ticket_amount,
    CASE
        WHEN  EXTRACT(week FROM arrival_time ::date) in (EXTRACT(week FROM festival_date::date))
        THEN EXTRACT(week FROM festival_date::date)
        ELSE '0'
    END AS  festival_week,
    CASE
        WHEN  EXTRACT(week FROM arrival_time ::date) in (EXTRACT(week FROM festival_date::date))
        THEN  festival_name
        ELSE ''
    END as festival_name
FROM
    flights
INNER join airports ON airports.airport_code  = flights.arrival_airport
INNER join ticket_flights ON ticket_flights.flight_id = flights.flight_id
INNER join festivals ON festivals.festival_city = airports.city
WHERE
     airports.city = 'Москва' AND  arrival_time::date BETWEEN '2018-07-23' AND '2018-09-30'
GROUP BY
    festival_date, festival_name, week_number
ORDER BY
    week_number