CREATE database pet;

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

-- Создаем таблицы, чтобы потом загрузить в них данные из таблиц GreenPlum

-- Таблица user из GP

CREATE TABLE pet.core_user (
    user_id Int32,
    name String,
    age Int32,
    email String,
    registration_date Date
)
ENGINE = MergeTree
ORDER BY user_id;

-- Таблица course из GP
CREATE TABLE pet.core_course (
    course_id Int32,
    title String,
    category String
)
ENGINE = MergeTree
ORDER BY course_id;

-- Таблица lesson из GP
CREATE TABLE pet.core_lesson (
    lesson_id Int32,
    title String,
    duration_min Int32,
    course_id Int32
)
ENGINE = MergeTree
ORDER BY lesson_id;

-- Таблица fact_lesson_views из GP

CREATE TABLE pet.core_fact_lesson_views (
    user_id Int32, 
    lesson_id Int32,
    course_id Int32,
    viewed_at DateTime64(3)
)
ENGINE = MergeTree
ORDER BY user_id;

-- Таблица enrollments из GP

CREATE TABLE pet.core_enrollments (
	id Int32,
    user_id Int32,
    course_id Int32,
    enrolled_at Date
)
ENGINE = MergeTree
ORDER BY user_id;

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

-- Создаем пустую таблицу lesson_popularity_summary(структуру витрины)

CREATE TABLE pet.lesson_popularity_summary
(
    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 = MergeTree
ORDER BY (lesson_id, course_id);

-- Создаем Materialized View

CREATE MATERIALIZED VIEW pet.mv_lesson_popularity_summary
TO pet.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 pet.core_fact_lesson_views AS flv
JOIN pet.core_lesson  AS l ON flv.lesson_id = l.lesson_id
JOIN pet.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 pet.lesson_popularity_summary

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