BEGIN;

CREATE MATERIALIZED VIEW platform_summary AS 
SELECT
    (SELECT COUNT(*) FROM users) AS total_users,
    (SELECT COUNT(*) FROM courses) AS total_courses,
    (SELECT COUNT(*) FROM lessons) AS total_lessons,
    (SELECT COUNT(DISTINCT user_id) FROM lesson_views) AS users_with_views,
    ROUND(
        (SELECT COUNT(*)::DECIMAL FROM lessons) / 
        NULLIF((SELECT COUNT(DISTINCT course_id) FROM lessons), 0), 
        2
    ) AS avg_lessons_per_course,
    ROUND(
        (SELECT COUNT(*)::DECIMAL FROM lesson_views) / 
        NULLIF((SELECT COUNT(DISTINCT lesson_id) FROM lesson_views), 0), 
        2
    ) AS avg_views_per_lesson;

COMMIT;