create table users (
id INT primary key,
name VARCHAR(50) NOT NULL,
age INT,
email VARCHAR(50) NOT NULL,
registration_date date
);

INSERT INTO users (id, name, age, email, registration_date)
VALUES
(1, 'Alice', 25, 'alice@mail.com', '2023-01-10'),
(2, 'Bob', 30, 'bob@gmail.com', '2023-02-05'),
(3, 'Charlie', 22, 'charlie@mail.com', '2023-02-20'),
(4, 'Diana', 28, 'diana@mail.com', '2023-03-01'),
(5, 'Ethan', 35, 'ethan@gmail.com', '2023-03-10'),
(6, 'Frank', 29, 'frank@mail.com', '2023-01-05'),
(7, 'Grace', 26, 'grace@gmail.com', '2023-01-12'),
(8, 'Henry', 32, 'henry@mail.com', '2023-01-20'),
(9, 'Iris', 24, 'iris@gmail.com', '2023-02-10'),
(10, 'Jack', 27, 'jack@mail.com', '2023-04-15'),
(11, 'Kelly', 23, 'kelly@gmail.com', '2023-04-20'),
(12, 'Leo', 31, 'leo@mail.com', '2023-01-15'),
(13, 'Mia', 26, 'mia@gmail.com', '2023-01-18'),
(14, 'Nina', 28, 'nina@mail.com', '2023-01-08'),
(15, 'Oscar', 33, 'oscar@gmail.com', '2023-01-10'),
(16, 'Paul', 29, 'paul@mail.com', '2023-02-15'),
(17, 'Quinn', 24, 'quinn@gmail.com', '2023-03-20'),
(18, 'Rita', 27, 'rita@mail.com', '2023-04-01'),
(19, 'Sam', 30, 'sam@gmail.com', '2023-04-10'),
(20, 'Tina', 25, 'tina@mail.com', '2023-04-18');

create table courses (
id INT primary key, 
title VARCHAR(100), 
category VARCHAR(50), 
created_at date
);

INSERT INTO courses (id, title, category, created_at)
VALUES
(1, 'SQL для начинающих', 'data', '2023-01-01'),
(2, 'Python для анализа данных', 'programming', '2023-01-15'),
(3, 'BI с нуля', 'business', '2023-03-01'),
(4, 'Excel для аналитиков', 'business', '2023-02-01'),
(5, 'Основы машинного обучения', 'data', '2023-03-15');


create table lessons (
id INT primary key,
course_id INT,
title VARCHAR(100),
duration_min INT,
foreign key (course_id) references courses(id)
);

INSERT INTO lessons (id, course_id, title, duration_min)
VALUES
(1, 1, 'SELECT и FROM', 10),
(2, 1, 'JOIN', 15),
(3, 1, 'WHERE и фильтрация', 12),
(4, 1, 'Агрегации и GROUP BY', 18),
(5, 1, 'Подзапросы', 25),
(6, 2, 'Pandas основы', 20),
(7, 2, 'NumPy', 15),
(8, 2, 'Визуализация данных', 22),
(9, 3, 'Основы BI', 12),
(10, 3, 'Метрики и дашборды', 18),
(11, 3, 'Power BI введение', 20),
(12, 4, 'Формулы в Excel', 15),
(13, 4, 'Сводные таблицы', 18),
(14, 4, 'Графики и диаграммы', 14),
(15, 5, 'Введение в ML', 20),
(16, 5, 'Линейная регрессия', 30),
(17, 5, 'Классификация', 28),
(18, 5, 'Кластеризация', 25);

create table enrollments (
id INT primary key,
user_id INT,
course_id INT,
enrolled_at date,
foreign key (user_id) references users(id),
foreign key (course_id) references courses(id)
);

INSERT INTO enrollments (id, user_id, course_id, enrolled_at)
VALUES
(1, 1, 1, '2023-01-15'),
(2, 1, 2, '2023-02-01'),
(3, 2, 1, '2023-01-20'),
(4, 3, 2, '2023-03-05'),
(5, 4, 3, '2023-04-01'),
(6, 6, 1, '2023-01-06'),
(7, 6, 2, '2023-01-10'),
(8, 6, 4, '2023-02-05'),
(9, 7, 1, '2023-01-13'),
(10, 7, 3, '2023-03-10'),
(11, 8, 1, '2023-01-22'),
(12, 8, 2, '2023-01-22'),
(13, 8, 3, '2023-01-22'),
(14, 9, 4, '2023-02-12'),
(15, 10, 1, '2023-04-16'),
(16, 11, 2, '2023-04-21'),
(17, 12, 1, '2023-01-16'),
(18, 13, 2, '2023-01-19'),
(19, 13, 4, '2023-02-20'),
(20, 14, 1, '2023-01-09'),
(21, 14, 2, '2023-01-09'),
(22, 14, 3, '2023-01-09'),
(23, 14, 4, '2023-02-01'),
(24, 14, 5, '2023-03-20'),
(25, 15, 1, '2023-01-11'),
(26, 15, 3, '2023-03-05'),
(27, 16, 2, '2023-02-16'),
(28, 16, 4, '2023-02-16'),
(29, 17, 3, '2023-03-22'),
(30, 17, 5, '2023-03-25'),
(31, 18, 1, '2023-04-02'),
(32, 19, 1, '2023-04-11'),
(33, 19, 2, '2023-04-11'),
(34, 20, 2, '2023-04-19'),
(35, 5, 5, '2023-03-20'),
(36, 1, 4, '2023-02-10'),
(37, 2, 3, '2023-03-15'),
(38, 3, 1, '2023-02-25'),
(39, 4, 2, '2023-03-10'),
(40, 6, 3, '2023-03-08'),
(41, 7, 2, '2023-02-01'),
(42, 9, 1, '2023-02-15'),
(43, 12, 3, '2023-03-10'),
(44, 15, 2, '2023-02-01'),
(45, 18, 4, '2023-04-05');

create table lesson_views (
id INT primary key,
user_id INT,
lesson_id INT,
viewed_at timestamp,
foreign key (user_id) references users(id),
foreign key (lesson_id) references lessons(id)
);

INSERT INTO lesson_views (id, user_id, lesson_id, viewed_at)
VALUES
(1, 1, 1, '2023-01-16 10:00:00'),
(2, 1, 2, '2023-01-16 10:15:00'),
(3, 1, 3, '2023-01-17 09:00:00'),
(4, 1, 4, '2023-01-17 09:30:00'),
(5, 1, 4, '2023-01-17 11:00:00'),
(6, 1, 4, '2023-01-18 10:00:00'),
(7, 1, 6, '2023-02-02 14:00:00'),
(8, 1, 12, '2023-02-15 10:00:00'),
(9, 1, 13, '2023-02-15 10:30:00'),
(10, 2, 1, '2023-01-21 09:00:00'),
(11, 2, 9, '2023-03-16 10:00:00'),
(12, 2, 10, '2023-03-16 10:30:00'),
(13, 3, 6, '2023-03-06 12:00:00'),
(14, 3, 1, '2023-02-26 11:00:00'),
(15, 3, 2, '2023-02-26 11:20:00'),
(16, 4, 9, '2023-04-02 10:00:00'),
(17, 4, 10, '2023-04-03 10:00:00'),
(18, 4, 6, '2023-03-12 14:00:00'),
(19, 4, 7, '2023-03-13 09:00:00'),
(20, 5, 15, '2023-03-21 10:00:00'),
(21, 5, 16, '2023-03-22 11:00:00'),
(22, 6, 1, '2023-01-07 10:00:00'),
(23, 6, 2, '2023-01-07 10:15:00'),
(24, 6, 3, '2023-01-08 09:00:00'),
(25, 6, 4, '2023-01-08 09:30:00'),
(26, 6, 5, '2023-01-09 10:00:00'),
(27, 6, 6, '2023-01-11 14:00:00'),
(28, 6, 7, '2023-01-12 10:00:00'),
(29, 6, 8, '2023-01-13 11:00:00'),
(30, 6, 12, '2023-02-06 09:00:00'),
(31, 6, 13, '2023-02-06 09:30:00'),
(32, 6, 14, '2023-02-07 10:00:00'),
(33, 6, 9, '2023-03-09 11:00:00'),
(34, 7, 1, '2023-01-14 10:00:00'),
(35, 7, 2, '2023-01-14 10:20:00'),
(36, 7, 3, '2023-01-15 09:00:00'),
(37, 7, 9, '2023-03-11 14:00:00'),
(38, 7, 10, '2023-03-11 14:30:00'),
(39, 9, 12, '2023-02-13 10:00:00'),
(40, 9, 13, '2023-02-13 10:30:00'),
(41, 9, 1, '2023-02-16 11:00:00'),
(42, 12, 1, '2023-01-17 10:00:00'),
(43, 12, 2, '2023-01-17 10:20:00'),
(44, 12, 1, '2023-04-10 11:00:00'),
(45, 12, 3, '2023-04-10 11:30:00'),
(46, 12, 9, '2023-03-12 10:00:00'),
(47, 13, 6, '2023-01-20 14:00:00'),
(48, 13, 7, '2023-01-21 10:00:00'),
(49, 13, 12, '2023-02-21 09:00:00'),
(50, 14, 1, '2023-01-09 08:00:00'),
(51, 14, 2, '2023-01-09 08:15:00'),
(52, 14, 3, '2023-01-10 10:00:00'),
(53, 14, 4, '2023-01-10 10:30:00'),
(54, 14, 5, '2023-01-11 09:00:00'),
(55, 14, 6, '2023-01-10 14:00:00'),
(56, 14, 7, '2023-01-11 10:00:00'),
(57, 14, 8, '2023-01-12 11:00:00'),
(58, 14, 9, '2023-01-10 08:00:00');


---------------------------------------------------------
-- 1 задание Активные пользователи

create materialized view user_activity_summary AS
with enroll_count as (
					select u.id as user_id, u.name as user_name, 
					COUNT(e.course_id) as enrollment_count
					from users u
					join enrollments e on u.id = e.user_id
					group by u.id, u.name
					),
viewed_count as (
				select ec.user_id, ec.user_name, enrollment_count,
				COUNT(distinct lv.lesson_id) as viewed_lessons_count,
				MIN(lv.viewed_at) as first_view,
				MAX(lv.viewed_at) as last_view
				from enroll_count ec
				left join lesson_views lv on ec.user_id = lv.user_id
				group by ec.user_id, ec.user_name, enrollment_count
				),
possible_lessons as (		
					select u.id as user_id, COUNT(l.id) as poss_lessons 
					from users u
					left join enrollments e on u.id = e.user_id
					left join lessons l on e.course_id = l.course_id 
					group by u.id
					)
select vc.user_id, user_name, enrollment_count, viewed_lessons_count, first_view, last_view, 
ROUND(100.0 * viewed_lessons_count / pl.poss_lessons, 2) as engagement_rate
from viewed_count vc
left join possible_lessons pl on vc.user_id = pl.user_id
;