CREATE MATERIALIZED VIEW lesson_popularity_summary
ENGINE = SummingMergeTree()
ORDER BY (course_id, lesson_id) AS
SELECT 
    lv.lesson_id as lesson_id,
    l.title as lesson_title,
    lv.course_id as course_id,
    c.title as course_title,
    count() as total_views,
    uniq(lv.user_id) as unique_users,
    min(lv.viewed_at) as first_view,
    max(lv.viewed_at) as last_view
FROM fact_lesson_views lv
LEFT JOIN dim_lesson l ON lv.lesson_id = l.lesson_id
LEFT JOIN dim_course c ON lv.course_id = c.course_id
GROUP BY 
    lv.lesson_id,
    l.title,
    lv.course_id,
    c.title;