SELECT DISTINCT DATE_TRUNC('month', event_time)::date AS mnth
    , COUNT(event_id) OVER(PARTITION BY DATE_TRUNC('month', event_time)::date 
                    ORDER BY DATE_TRUNC('month', event_time)::date) AS count_month
    , COUNT(event_id) OVER(ORDER BY DATE_TRUNC('month', event_time)::date) AS count_month_cum
FROM tools_shop.events e
    JOIN tools_shop.users u ON e.user_id = u.user_id
    JOIN tools_shop.orders o ON u.user_id = o.user_id
WHERE event_name = 'view_item'