CREATE TABLE IF NOT EXISTS `users` (
  `id` INT(11) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
  `username` VARCHAR(255) NOT NULL UNIQUE,
  `email` VARCHAR(255) NOT NULL UNIQUE,
  `password` VARCHAR(255) NOT NULL,
  `role` VARCHAR(50) NOT NULL DEFAULT 'user',
  `created_at` TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);