-- Этап 1
-- Задание 1
-- Перенести данные как в пет-проекте с Greenplum

CREATE TABLE itikhomirov.core_user
ON CLUSTER clickhouse_cluster
(
    user_id Int32,
    name String,
    age Int32,
    email String,
    registration_date DateTime64(3, 'UTC')
)
ENGINE = ReplicatedMergeTree(
    '/clickhouse/tables/{shard}/itikhomirov/core_user',
    '{replica}'
)
ORDER BY user_id;

ALTER TABLE itikhomirov.core_user
MODIFY COLUMN registration_date DateTime64(3);

CREATE TABLE itikhomirov.core_lesson 
ON CLUSTER clickhouse_cluster
(
    lesson_id Int32,
    title String,
    duration_min Int32,
    course_id Int32
)
ENGINE = ReplicatedMergeTree(
    '/clickhouse/tables/{shard}/itikhomirov/core_lesson',
    '{replica}'
)
ORDER BY lesson_id;

CREATE TABLE itikhomirov.core_fact_lesson_views
ON CLUSTER clickhouse_cluster
(
	user_id Int32, 
    lesson_id Int32,
    course_id Int32,
    viewed_at DateTime64(3)
)
ENGINE = ReplicatedMergeTree(
    '/clickhouse/tables/{shard}/itikhomirov/core_fact_lesson_views',
    '{replica}'
)
ORDER BY user_id;

ALTER TABLE itikhomirov.core_fact_lesson_views
MODIFY COLUMN viewed_at DateTime64(3);

DROP TABLE IF EXISTS itikhomirov.core_fact_lesson_views
ON CLUSTER clickhouse_cluster;

CREATE TABLE itikhomirov.core_enrollments
ON CLUSTER clickhouse_cluster
(
	user_id Int32, 
    course_id Int32,
    enrolled_at DateTime64(3)
)
ENGINE = ReplicatedMergeTree(
    '/clickhouse/tables/{shard}/itikhomirov/core_enrollmentsы',
    '{replica}'
)
ORDER BY user_id;

CREATE TABLE itikhomirov.core_course
ON CLUSTER clickhouse_cluster
(
    course_id Int32,
    title String,
    category String
)
ENGINE = ReplicatedMergeTree(
    '/clickhouse/tables/{shard}/itikhomirov/core_course',
    '{replica}'
)
ORDER BY course_id;

-- Этап 2. Создание витринных таблиц
-- Задание 2: Подготовь структуру витрины lesson_popularity_summary

-- Создаем пустую таблицу lesson_popularity_summary(структуру витрины)

CREATE TABLE itikhomirov.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),
    last_view     DateTime64(3)
)
ENGINE = ReplicatedMergeTree(
    '/clickhouse/tables/{shard}/itikhomirov/lesson_popularity_summary',
    '{replica}'
)
ORDER BY (lesson_id, course_id);

-- Создаем Materialized View

DROP TABLE IF EXISTS itikhomirov.mv_lesson_popularity_summary
ON CLUSTER clickhouse_cluster;

CREATE MATERIALIZED VIEW itikhomirov.mv_lesson_popularity_summary
ON CLUSTER clickhouse_cluster
TO itikhomirov.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 itikhomirov.core_fact_lesson_views AS flv
JOIN itikhomirov.core_lesson  AS l ON flv.lesson_id = l.lesson_id
JOIN itikhomirov.core_course  AS c ON flv.course_id = c.course_id
GROUP BY
    flv.lesson_id,
    l.title,
    flv.course_id,
    c.title;

-- Вставляем данные в таблицу lesson_popularity_summary

INSERT INTO itikhomirov.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 itikhomirov.core_fact_lesson_views AS flv
JOIN itikhomirov.core_lesson  AS l ON flv.lesson_id = l.lesson_id
JOIN itikhomirov.core_course  AS c ON flv.course_id = c.course_id
GROUP BY
    flv.lesson_id,
    l.title,
    flv.course_id,
    c.title;

-- Задание 3: Создай витрину inactive_users_summary

-- Создаем пустую таблицу inactive_users_summary(структуру витрины)

DROP TABLE IF EXISTS itikhomirov.inactive_users_summary
ON CLUSTER clickhouse_cluster;

DROP TABLE IF EXISTS itikhomirov.inactive_users_summary
ON CLUSTER clickhouse_cluster;

CREATE TABLE itikhomirov.inactive_users_summary
ON CLUSTER clickhouse_cluster
(
    user_id UInt32,
    name String,
    email String,
    age UInt8,
    registered_courses_count UInt32,
    registration_date DateTime64(3)
)
ENGINE = ReplicatedMergeTree(
    '/clickhouse/tables/{shard}/itikhomirov/inactive_users_summary',
    '{replica}'
)
ORDER BY (user_id);

-- Создаем Materialized View

DROP TABLE IF EXISTS itikhomirov.mv_inactive_users_summary
ON CLUSTER clickhouse_cluster;

CREATE MATERIALIZED VIEW itikhomirov.mv_inactive_users_summary
ON CLUSTER clickhouse_cluster
TO itikhomirov.inactive_users_summary
AS
WITH user_courses AS (
    SELECT
        e.user_id,
        countDistinct(e.course_id) AS registered_courses_count
    FROM itikhomirov.core_enrollments AS e
    GROUP BY
        e.user_id
)
SELECT
    u.user_id                                AS user_id,
    u.name                                   AS name,
    u.email                                  AS email,
    u.age                                    AS age,
    coalesce(uc.registered_courses_count, 0) AS registered_courses_count,
    u.registration_date                      AS registration_date
FROM itikhomirov.core_user AS u
LEFT JOIN user_courses AS uc
    ON u.user_id = uc.user_id
WHERE u.user_id NOT IN (
    SELECT DISTINCT user_id
    FROM itikhomirov.core_fact_lesson_views
);


INSERT INTO itikhomirov.inactive_users_summary
WITH user_courses AS (
    SELECT
        e.user_id,
        countDistinct(e.course_id) AS registered_courses_count
    FROM itikhomirov.core_enrollments AS e
    GROUP BY
        e.user_id
)
-- В CTE user_courses считается число курсов по каждому пользователю независимо от просмотров
-- Снаружи берутся пользователи без просмотров (NOT IN по core_fact_lesson_views), 
-- и к ним подмешивается уже готовый registered_courses_count.
SELECT
    u.user_id AS user_id,
    u.name AS name,
    u.email AS email,
    u.age AS age,
    coalesce(uc.registered_courses_count, 0) AS registered_courses_count,
    u.registration_date AS registration_date
FROM itikhomirov.core_user AS u
LEFT JOIN user_courses AS uc
    ON u.user_id = uc.user_id
WHERE u.user_id NOT IN (
    SELECT DISTINCT user_id
    FROM itikhomirov.core_fact_lesson_views
)
ORDER BY u.user_id;

-- Задание 4: Создай витрину course_completion_rate

CREATE TABLE itikhomirov.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   Float32
)
ENGINE = ReplicatedMergeTree(
    '/clickhouse/tables/{shard}/itikhomirov/course_completion_rate',
    '{replica}'
)
ORDER BY (user_id, course_id);


-- Создаем Materialized View

CREATE MATERIALIZED VIEW itikhomirov.mv_course_completion_rate
ON CLUSTER clickhouse_cluster
TO itikhomirov.course_completion_rate
AS
WITH
lessons_per_course AS (
    SELECT
        course_id,
        countDistinct(lesson_id) AS lessons_in_course
    FROM itikhomirov.core_lesson
    GROUP BY course_id
),
views_per_user_course AS (
    SELECT
        user_id,
        course_id,
        countDistinct(lesson_id) AS lessons_viewed
    FROM itikhomirov.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,
    lpc.lessons_in_course AS lessons_in_course,
    coalesce(vpc.lessons_viewed, 0) AS lessons_viewed,
    ROUND(
        COALESCE(
            NULLIF(coalesce(vpc.lessons_viewed, 0) * 1.0, 0)
            / NULLIF(lpc.lessons_in_course * 1.0, 0),
            0
        ),
        2
    ) AS completion_rate
FROM itikhomirov.core_user AS u
JOIN itikhomirov.core_enrollments AS e ON u.user_id  = e.user_id
JOIN itikhomirov.core_course AS c ON e.course_id = c.course_id
JOIN lessons_per_course AS lpc ON c.course_id = lpc.course_id
LEFT JOIN views_per_user_course AS vpc ON vpc.user_id   = u.user_id AND vpc.course_id = c.course_id
ORDER BY
    u.user_id,
    c.course_id;

-- Вставляем данные в таблицу pet.course_completion_rate

INSERT INTO itikhomirov.course_completion_rate
-- Создаем две временные таблицы:
-- 1) Сколько уроков в каждом курсе
WITH
lessons_per_course AS (
    SELECT
        course_id,
        countDistinct(lesson_id) AS lessons_in_course
    FROM itikhomirov.core_lesson
    GROUP BY course_id
),
-- 2) Сколько уроков каждого курса посмотрел пользователь
views_per_user_course AS (
    SELECT
        user_id,
        course_id,
        countDistinct(lesson_id) AS lessons_viewed
    FROM itikhomirov.core_fact_lesson_views
    GROUP BY user_id, course_id
)
-- Основной запрос
SELECT
    u.user_id AS user_id, 
    u.name AS user_name,
    c.course_id AS course_id,
    c.title AS course_title,
    lpc.lessons_in_course AS lessons_in_course,
    coalesce(vpc.lessons_viewed, 0) AS lessons_viewed,
    ROUND(
        COALESCE(
            NULLIF(coalesce(vpc.lessons_viewed, 0) * 1.0, 0)
            / NULLIF(lpc.lessons_in_course * 1.0, 0),
            0
        ),
        2
    ) AS completion_rate
FROM itikhomirov.core_user AS u
JOIN itikhomirov.core_enrollments AS e ON u.user_id  = e.user_id
JOIN itikhomirov.core_course AS c ON e.course_id = c.course_id
JOIN lessons_per_course AS lpc ON c.course_id = lpc.course_id
LEFT JOIN views_per_user_course AS vpc ON vpc.user_id   = u.user_id AND vpc.course_id = c.course_id
ORDER BY
    u.user_id,
    c.course_id;

-- Этап 3. Анализ и запросы

-- Задание 5: Напиши SQL-запросы к витринам

-- Уроки с хотя бы одним просмотром
SELECT
    lesson_title,
    course_title,
    total_views
FROM itikhomirov.lesson_popularity_summary
WHERE total_views > 0
ORDER BY lesson_title ASC;

-- Топ‑3 урока внутри одного курса
SELECT
    lesson_title,
    course_title,
    total_views
FROM itikhomirov.lesson_popularity_summary
WHERE course_title = 'SQL для начинающих'
ORDER BY total_views DESC
LIMIT 3;

-- Пользователи, которые завершили курсы на 100%
SELECT
    user_id,
    user_name,
    course_title,
    completion_rate
FROM itikhomirov.course_completion_rate
WHERE completion_rate = 1
ORDER BY user_id;

-- Этап 4. Тестирование и валидация

-- 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"**

SELECT
    sum(total_views)                 AS sum_total_views,
    avg(total_views)                 AS avg_total_views,
    min(total_views)                 AS min_total_views,
    max(total_views)                 AS max_total_views
FROM itikhomirov.lesson_popularity_summary
WHERE lesson_id IN (1, 3, 5);

SELECT
    sum(total_views)                 AS sum_total_views,
    avg(total_views)                 AS avg_total_views,
    min(total_views)                 AS min_total_views,
    max(total_views)                 AS max_total_views
FROM itikhomirov.lesson_popularity_summary
WHERE lesson_id = 999;

-- Отчёт в .doc файле