--ПЕТ ПРОЕКТ СОЗДАНИЕ ТАБЛИЦ

CREATE TABLE bhabibullin.core_enrollments
ON CLUSTER clickhouse_cluster
(
	user_id 	UInt32,
	course_id 	UInt32,
	enrolled_at	DateTime
)
ENGINE = ReplicatedMergeTree(
	'/clickhouse/tables/{shard}/bhabibullin/core_enrollments',
	'{replica}'
)
ORDER BY (user_id, enrolled_at);


CREATE TABLE bhabibullin.core_dim_user
ON CLUSTER clickhouse_cluster
(
	user_id 	 	  UInt32,
	name 			  String,
	age			   	  UInt32,
	email 			  String,
	registration_date Date
)
ENGINE = ReplicatedMergeTree(
	'/clickhouse/tables/{shard}/bhabibullin/core_dim_user',
	'{replica}'
)
ORDER BY (user_id, registration_date);


CREATE TABLE bhabibullin.core_fact_lesson_views
ON CLUSTER clickhouse_cluster
(
    user_id   UInt32, 
    lesson_id UInt32,
    course_id UInt32,
    viewed_at DateTime64(3)
)
ENGINE = ReplicatedMergeTree(
    '/clickhouse/tables/{shard}/bhabibullin/core_fact_lesson_views',
    '{replica}'
)
ORDER BY user_id;

CREATE TABLE bhabibullin.core_dim_course
ON CLUSTER clickhouse_cluster
(
	course_id	UInt32,
	title	 	String,
	category	String
)
ENGINE = ReplicatedMergeTree(
    '/clickhouse/tables/{shard}/bhabibullin/core_dim_course',
    '{replica}'
)
ORDER BY course_id;

drop table bhabibullin.core_dim_course ;

CREATE TABLE bhabibullin.core_dim_lesson
ON CLUSTER clickhouse_cluster
(
	lesson_id		UInt32,
	title			String,
	duration_min	UInt32,
	course_id		UInt32
)
ENGINE = ReplicatedMergeTree(
	'/clickhouse/tables/{shard}/bhabibullin/core_dim_lesson',
	'{replica}'
)
ORDER BY (lesson_id, course_id);


-- Этап 2. Создание витринных таблиц
-- Задание 2: Подготовь структуру витрины lesson_popularity_summary
/*
- Спроектируй таблицу, где каждая строка — один урок.
- Для каждого урока должны храниться:
    - ID и название урока
    - ID и название курса, к которому он относится
    - Общее число просмотров
    - Количество уникальных пользователей, посмотревших урок
    - Дата первого и последнего просмотра
 */

CREATE TABLE bhabibullin.lesson_popularity_summary
ON CLUSTER clickhouse_cluster
(
    lesson_id     UInt32,
    lesson_title  String,
    course_id     UInt32,
    course_title  String,
    total_views   UInt32,
    unique_users  UInt32,
    first_view    DateTime64(3, 'UTC'),
    last_view     DateTime64(3, 'UTC')
)
ENGINE = ReplicatedMergeTree(
	'/clickhouse/tables/{shard}/bhabibullin/lesson_popularity_summary',
	'{replica}'
)
ORDER BY (lesson_id, course_id);

CREATE MATERIALIZED VIEW mv_lesson_popularity_summary
ON CLUSTER clickhouse_cluster
TO bhabibullin.lesson_popularity_summary
AS
SELECT
    flv.lesson_id AS lesson_id,
    l.title AS lesson_title,
    flv.course_id AS course_id,
    c.title AS course_title,
    count() AS total_views,
    uniqExact(flv.user_id) AS unique_users,
    min(flv.viewed_at) AS first_view,
    max(flv.viewed_at) AS last_view
FROM core_fact_lesson_views AS flv
JOIN core_dim_lesson  AS l ON flv.lesson_id = l.lesson_id
JOIN core_dim_course  AS c ON flv.course_id = c.course_id
GROUP BY
    flv.lesson_id,
    l.title,
    flv.course_id,
    c.title;

INSERT INTO bhabibullin.lesson_popularity_summary
SELECT
    flv.lesson_id,
    l.title AS lesson_title,
    flv.course_id,
    c.title AS course_title,
    count() AS total_views,
    uniqExact(flv.user_id) AS unique_users,
    min(flv.viewed_at) AS first_view,
    max(flv.viewed_at) AS last_view
FROM core_fact_lesson_views AS flv
JOIN core_dim_lesson  AS l ON flv.lesson_id = l.lesson_id
JOIN core_dim_course  AS c ON flv.course_id = c.course_id
GROUP BY
    flv.lesson_id,
    l.title,
    flv.course_id,
    c.title;

select * from bhabibullin.mv_lesson_popularity_summary ;
select * from bhabibullin.lesson_popularity_summary ;
show tables;

/*
 ### ✅ **Задание 3: Создай витрину `inactive_users_summary`**

**Цель:** выявить пользователей, которые **зарегистрировались, но ничего не посмотрели**.

📌 **Что нужно сделать:**

- Подготовь таблицу, где каждая строка — один такой "неактивный" пользователь.
- Для каждого пользователя нужны:
    - ID, имя, email, возраст
    - Количество курсов, на которые он записался
    - Дата регистрации

**Где пригодится:**

Эта витрина может использоваться для продуктовой аналитики, триггерных рассылок (например, напоминаний), анализа оттока, повышения вовлечённости.
 */ 

DROP TABLE bhabibullin.inactive_users_summary;
DROP VIEW bhabibullin.mv_inactive_users_summary ;
show tables;

CREATE TABLE bhabibullin.inactive_users_summary
ON CLUSTER clickhouse_cluster
(
	user_id  		  UInt32,
	name		      String,
	email 		      String,
	age 		      UInt32,
	enrollment_count  UInt32,
	registration_date Date
)
ENGINE = ReplicatedMergeTree(
	'/clickhouse/tables/{shard}/bhabibullin/inactive_users_summary',
	'{replica}'
)
ORDER BY user_id;

CREATE MATERIALIZED VIEW bhabibullin.mv_inactive_users_summary 
ON CLUSTER clickhouse_cluster
to bhabibullin.inactive_users_summary 
AS
SELECT  
    cdu.user_id,
    cdu.name,
    cdu.email,
    cdu.age,
    0 as enrollment_count,
    cdu.registration_date
FROM core_dim_user cdu 
WHERE (cdu.user_id, 1) NOT IN (
    SELECT user_id, 1 
    FROM core_enrollments
    GROUP BY user_id
);

INSERT INTO bhabibullin.inactive_users_summary
SELECT  
	cdu.user_id,
    cdu.name,
    cdu.email,
    cdu.age,
    0 as enrollment_count,
    cdu.registration_date
FROM core_dim_user cdu 
WHERE (cdu.user_id, 1) NOT IN (
    SELECT user_id, 1 
    FROM core_enrollments
    GROUP BY user_id
);

select * from bhabibullin.inactive_users_summary ius ;
select * from bhabibullin.mv_inactive_users_summary mius ;

/*
 ### ✅ **Задание 4: Создай витрину `course_completion_rate`**

**Цель:** проанализировать, насколько хорошо пользователи проходят курсы.

📌 **Что нужно сделать:**

- Сформируй таблицу, где строка — это пользователь + курс.
- Для каждой пары нужно рассчитать:
    - Общее число уроков в курсе
    - Сколько из них просмотрел конкретный пользователь
    - Коэффициент завершения (`lessons_viewed / lessons_in_course`)
 */

CREATE TABLE IF NOT EXISTS bhabibullin.course_completion_rate
ON CLUSTER clickhouse_cluster
(
    user_id         UInt32,
    user_name       String,
    course_id       UInt32,
    course_title    String,
    lessons_in_course UInt32,
    lessons_viewed  UInt32,
    completion_rate Float64
)
ENGINE = ReplicatedMergeTree(
	'/clickhouse/tables/{shard}/bhabibullin/course_completion_rate',
	'{replica}'
)
ORDER BY (user_id, course_id);


CREATE MATERIALIZED VIEW IF NOT EXISTS bhabibullin.mv_course_completion_rate
ON CLUSTER clickhouse_cluster
TO bhabibullin.course_completion_rate
AS
WITH lessons_in_course AS (
    SELECT
        course_id,
        count(Distinct lesson_id) AS lessons_in_course
    FROM core_dim_lesson
    GROUP BY course_id
),
views_user_course AS (
    SELECT
        user_id,
        course_id,
        count(Distinct lesson_id) AS lessons_viewed
    FROM core_fact_lesson_views
    GROUP BY user_id, course_id
)
SELECT
    u.user_id AS user_id, 
    u.name AS user_name,
    c.course_id AS course_id,
    c.title AS course_title,
    lic.lessons_in_course AS lessons_in_course,
    coalesce(vuc.lessons_viewed, 0) AS lessons_viewed,
    ROUND(
        COALESCE(
            NULLIF(coalesce(vuc.lessons_viewed, 0) * 1.0, 0)
            / NULLIF(lic.lessons_in_course * 1.0, 0),
            0
        ),
        2
    ) AS completion_rate
FROM core_dim_user u
JOIN core_enrollments e ON u.user_id  = e.user_id
JOIN core_dim_course c ON e.course_id = c.course_id
JOIN lessons_in_course AS lic ON c.course_id = lic.course_id
LEFT JOIN views_user_course AS vuc ON vuc.user_id   = u.user_id AND vuc.course_id = c.course_id
ORDER BY
    u.user_id,
    c.course_id;

INSERT INTO bhabibullin.course_completion_rate 
WITH lessons_in_course AS (
    SELECT
        course_id,
        count(Distinct lesson_id) AS lessons_in_course
    FROM core_dim_lesson
    GROUP BY course_id
),
views_user_course AS (
    SELECT
        user_id,
        course_id,
        count(Distinct lesson_id) AS lessons_viewed
    FROM core_fact_lesson_views
    GROUP BY user_id, course_id
)
SELECT
    u.user_id AS user_id, 
    u.name AS user_name,
    c.course_id AS course_id,
    c.title AS course_title,
    lic.lessons_in_course AS lessons_in_course,
    coalesce(vuc.lessons_viewed, 0) AS lessons_viewed,
    ROUND(
        COALESCE(
            NULLIF(coalesce(vuc.lessons_viewed, 0) * 1.0, 0)
            / NULLIF(lic.lessons_in_course * 1.0, 0),
            0
        ),
        2
    ) AS completion_rate
FROM core_dim_user u
JOIN core_enrollments e ON u.user_id  = e.user_id
JOIN core_dim_course c ON e.course_id = c.course_id
JOIN lessons_in_course AS lic ON c.course_id = lic.course_id
LEFT JOIN views_user_course AS vuc ON vuc.user_id   = u.user_id AND vuc.course_id = c.course_id;

select * from bhabibullin.course_completion_rate;
select * from bhabibullin.mv_course_completion_rate;

/*
 # 📊 Этап 3. Анализ и запросы

### ✅ **Задание 5: Напиши SQL-запросы к витринам**

**Напиши свои вариации для практики.**
 */

--Топ-5 самых просматриваемых уроков
SELECT 
    lesson_title,
    course_title,
    total_views
FROM lesson_popularity_summary
ORDER BY total_views DESC
LIMIT 5;

--Неактивные пользователи, записавшиеся на курсы
SELECT 
    name,
    email,
    enrollment_count
FROM inactive_users_summary
WHERE enrollment_count > 0
ORDER BY registration_date DESC;

--Курсы с самым высоким процентом завершения
SELECT 
    course_title,
    AVG(completion_rate) AS avg_completion
FROM course_completion_rate
GROUP BY course_title
ORDER BY avg_completion DESC
LIMIT 5;

-- топ 5 курсов по количеству уникальных пользователей
SELECT
    course_title,
    unique_users
FROM lesson_popularity_summary
ORDER BY unique_users DESC
LIMIT 5;

--новые пользователи за прошлый месяц 
SELECT
    user_id,
    name,
    email,
    registration_date
FROM core_dim_user
WHERE registration_date >= today() - INTERVAL 30 DAY
ORDER BY registration_date DESC;

/*
 ### ✅ **Задание 6: Сравни данные с Greenplum**
  
1. Выбери 2–3 значения из таблиц `_summary_source` в Greenplum
2. Сравни с ClickHouse-результатами:
    - Совпадает ли `SUM`, `AVG`, `MIN`, `MAX`
    - Проверяй `NULL`, `0`, округления
3. Напиши мини-отчёт: **"где совпадает, где нет, почему"

Совпадает ли SUM, AVG, MIN, MAX
Совпадает и в гринплам, и в кликхаус

Проверяй NULL, 0, округления
С этим даже траблы были при пет проекте, кликхаус тяжело обрабатывает нулл значения
*/