CREATE TABLE `users`(
`id` INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
`username` VARCHAR(30) NOT NULL UNIQUE,
`password` VARCHAR(30) NOT NULL,
`email` VARCHAR(50) NOT NULL
);

CREATE TABLE `categories`(
`id` INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
`category` VARCHAR(30) NOT NULL
);

CREATE TABLE `articles`(
`id` INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
`title` VARCHAR(50) NOT NULL,
`content` TEXT NOT NULL,
`category_id` INT,
CONSTRAINT `fk_articles_categories`
FOREIGN KEY (`category_id`)
REFERENCES `categories`(`id`)
);

CREATE TABLE `users_articles`(
`user_id` INT,
`article_id` INT,
PRIMARY KEY (`user_id`,`article_id`),
CONSTRAINT `fk_users_articles_users`
FOREIGN KEY (`user_id`)
REFERENCES `users`(`id`),
CONSTRAINT `fk_users_articles_articles`
FOREIGN KEY (`article_id`)
REFERENCES `articles`(`id`)
);

CREATE TABLE `comments`(
`id` INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
`comment` VARCHAR(255) NOT NULL,
`article_id` INT NOT NULL,
`user_id` INT NOT NULL,
CONSTRAINT `fk_comments_articles`
FOREIGN KEY (`article_id`)
REFERENCES `articles`(`id`),
CONSTRAINT `fk_comments_users`
FOREIGN KEY (`user_id`)
REFERENCES `users`(`id`)
);

CREATE TABLE `likes`(
`id` INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
`article_id` INT,
`comment_id` INT,
`user_id` INT NOT NULL,
CONSTRAINT `fk_likes_articles`
FOREIGN KEY (`article_id`)
REFERENCES `articles`(`id`),
CONSTRAINT `fk_likes_comments`
FOREIGN KEY (`comment_id`)
REFERENCES `comments`(`id`), 
CONSTRAINT `fk_likes_users`
FOREIGN KEY (`user_id`)
REFERENCES `users`(`id`)
);