BEGIN;

CREATE TABLE SKONEV.users(
	id INT PRIMARY KEY, 
	name VARCHAR(100), 
	age INT, 
	email VARCHAR(255) UNIQUE, 
	registration_date DATE NOT NULL
	);

CREATE TABLE SKONEV.courses(
	id INT PRIMARY KEY,
	title TEXT NOT NULL,
	category VARCHAR(255) CHECK (category IN ('data', 'programming', 'business')),
	created_at DATE NOT NULL
	);

CREATE TABLE SKONEV.lessons(
	id INT PRIMARY KEY, 
	course_id INT NOT NULL,
	FOREIGN KEY (course_id) REFERENCES courses(id), 
	title TEXT NOT NULL, 
	duration_min INT NOT NULL
	);


CREATE TABLE SKONEV.enrollments(
	id INT PRIMARY KEY, 
	user_id INT NOT NULL,
	FOREIGN KEY (user_id) REFERENCES users(id), 
	course_id INT NOT NULL,
	FOREIGN KEY (course_id) REFERENCES courses(id), 
	enrolled_at DATE NOT NULL
	);

CREATE TABLE SKONEV.lesson_views(
	id INT PRIMARY KEY, 
	user_id INT NOT NULL,
	FOREIGN KEY (user_id) REFERENCES users(id), 
	lesson_id INT NOT NULL,
	FOREIGN KEY (lesson_id) REFERENCES lessons(id), 
	viewed_at TIMESTAMP NOT NULL
	);

COMMIT;