CREATE VIEW sessions_statistics AS
SELECT
    s.session_id,
    s.begin_at,
    s.ticket_price,
    h.hall_id,
    h.hall_name,
    h.capacity AS total_seats,
    m.movie_id,
    m.title AS movie_title,
    m.duration,
    g.genre_id,
    g.genre_name,
    COUNT(t.ticket_id) AS sold_tickets,
    COUNT(r.refund_id) AS refunded_tickets,
    SUM(CASE WHEN t.ticket_id IS NOT NULL THEN s.ticket_price ELSE 0 END) AS sales_revenue,
    SUM(CASE WHEN r.refund_id IS NOT NULL THEN r.refund_amount ELSE 0 END) AS refund_expenses
FROM halls h
JOIN sessions s 
    ON s.hall_id = h.hall_id
JOIN movies m
    ON s.movie_id = m.movie_id
JOIN genres g
    ON m.genre_id = g.genre_id
LEFT JOIN tickets t 
    ON t.session_id = s.session_id
LEFT JOIN refunds r
    ON r.ticket_id = t.ticket_id
GROUP BY
    s.session_id;