-- Этап 3. Анализ и запросы - Напиши SQL-запросы к витринам
-- Напиши свои вариации для практики--


-- Топ-5 самых просматриваемых уроков

SELECT 
    lesson_title,
    course_title,
    total_views
FROM dsolovianov.lesson_popularity_summary
ORDER BY total_views DESC
LIMIT 5;


-- Неактивные пользователи, записавшиеся на курсы

SELECT 
    name,
    email,
    registered_courses_count
FROM dsolovianov.inactive_users_summary
WHERE registered_courses_count > 0
ORDER BY registration_date DESC;

-- Курсы с самым высоким процентом завершения

SELECT 
    course_title,
    AVG(completion_rate) AS avg_completion
FROM dsolovianov.course_completion_rate
GROUP BY course_title
ORDER BY avg_completion DESC
LIMIT 5;

-- Мои вариации --

-- Среднее количество учеников на урок по каждому курсу

SELECT 
    course_title,
    ROUND(AVG(unique_users), 2) AS avg_users_lesson,
    SUM(total_views) AS total_course_views
FROM dsolovianov.lesson_popularity_summary
GROUP BY course_title
ORDER BY avg_users_lesson DESC;

-- Возрастное распределение неактивных пользователей

SELECT 
    CASE 
        WHEN age < 25 THEN 'до 25'
        WHEN age BETWEEN 25 AND 30 THEN '25-30'
        WHEN age BETWEEN 31 AND 35 THEN '31-35'
        ELSE '35+'
    END AS age_group,
    COUNT(*) AS inactive_users_count,
    AVG(registered_courses_count) AS avg_courses_enrolled
FROM dsolovianov.inactive_users_summary
GROUP BY age_group
ORDER BY age_group;

-- Пользователи, которые начали, но не закончили курс (completion_rate между 0 и 1)

SELECT 
    user_name,
    course_title,
    lessons_viewed,
    lessons_in_course,
    ROUND(completion_rate * 100, 0) AS no_completion,
    (lessons_in_course - lessons_viewed) AS remaining_lessons
FROM dsolovianov.course_completion_rate
WHERE completion_rate BETWEEN 0.01 AND 0.99
ORDER BY completion_rate DESC, user_name;

-- Прогресс каждого пользователя по курсам (с указанием статуса)

SELECT 
    user_name,
    course_title,
    lessons_viewed,
    lessons_in_course,
    ROUND(completion_rate * 100, 0) AS progress_percent,
    CASE 
        WHEN completion_rate = 1.0 THEN 'Пройден'
        WHEN completion_rate = 0 THEN 'Не начат'
        WHEN completion_rate >= 0.5 THEN 'В процессе (>50%)'
        ELSE 'В процессе (<50%)'
    END AS status
FROM dsolovianov.course_completion_rate
ORDER BY user_name, completion_rate DESC;