CREATE TABLE IF NOT EXISTS amaksatov.users (
    id SERIAL PRIMARY KEY,
    name VARCHAR(100),
    age INT,
    email VARCHAR(255),
    registration_date DATE
);

CREATE TABLE IF NOT EXISTS amaksatov.courses (
    id SERIAL PRIMARY KEY,
    title VARCHAR(255),
    category VARCHAR(100),
    created_at DATE
);

CREATE TABLE IF NOT EXISTS amaksatov.lessons (
    id SERIAL PRIMARY KEY,
    course_id INT,
    title VARCHAR(255),
    duration_min INT,
    FOREIGN KEY (course_id) REFERENCES amaksatov.courses(id)
);

CREATE TABLE IF NOT EXISTS amaksatov.enrollments (
    id SERIAL PRIMARY KEY,
    user_id INT,
    course_id INT,
    enrolled_at date,
    FOREIGN KEY (user_id) REFERENCES amaksatov.users(id),
    FOREIGN KEY (course_id) REFERENCES amaksatov.courses(id)
);

CREATE TABLE IF NOT EXISTS amaksatov.lesson_views (
    id SERIAL PRIMARY KEY,
    user_id INT,
    lesson_id INT,
    viewed_at TIMESTAMP,
    FOREIGN KEY (user_id) REFERENCES amaksatov.users(id),
    FOREIGN KEY (lesson_id) REFERENCES amaksatov.lessons(id)
);


INSERT
    INTO
    amaksatov.users (
        name,
        age,
        email,
        registration_date
    )
VALUES (
    'Alice',
    25,
    'alice@mail.com',
    '2023-01-10'
),
(
    'Bob',
    30,
    'bob@gmail.com',
    '2023-02-05'
),
(
    'Charlie',
    22,
    'charlie@mail.com',
    '2023-02-20'
),
(
    'Diana',
    28,
    'diana@mail.com',
    '2023-03-01'
),
(
    'Ethan',
    35,
    'ethan@gmail.com',
    '2023-03-10'
);

SELECT * FROM amaksatov.users;


INSERT
    INTO
    amaksatov.courses (
        title,
        category,
        created_at
    )
VALUES 
(
    'SQL для начинающих',
    'data',
    '2023-01-01'
),
(
    'Python для анализа данных',
    'programming',
    '2023-01-15'
),
(
    'BI с нуля',
    'business',
    '2023-03-01'
);

INSERT
    INTO
    amaksatov.lessons (
        course_id,
        title,
        duration_min
    )
VALUES
(
    1,
    'SELECT и FROM',
    10
),
(
    1,
    'JOIN',
    15
),
(
    2,
    'Pandas',
    20
),
(
    3,
    'Основы BI',
    12
),
(
    3,
    'Метрики и дашборды',
    18
);

INSERT
    INTO
    amaksatov.enrollments (
        user_id,
        course_id,
        enrolled_at
    )
VALUES
(
    1,
    1,
    '2023-01-15'
),
(
    1,
    2,
    '2023-02-01'
),
(
    2,
    1,
    '2023-01-20'
),
(
    3,
    2,
    '2023-03-05'
),
(
    4,
    3,
    '2023-04-01'
);

INSERT
    INTO
    amaksatov.lesson_views (
        user_id,
        lesson_id,
        viewed_at
    )
VALUES
(
    1,
    1,
    '2023-01-16 10:00:00'
),
(
    1,
    2,
    '2023-01-16 10:15:00'
),
(
    2,
    1,
    '2023-01-21 09:00:00'
),
(
    3,
    3,
    '2023-03-06 12:00:00'
),
(
    4,
    4,
    '2023-04-02 10:00:00'
),
(
    4,
    5,
    '2023-04-03 10:00:00'
);