DROP TABLE IF EXISTS `notifications`;
CREATE TABLE `notifications` (
  `notification_id` INT NOT NULL AUTO_INCREMENT,
  `notification_type` INT NOT NULL,
  `user_id` INT NOT NULL,
  `product_id` INT,
  `is_seen` BOOLEAN DEFAULT FALSE,
  `seen_timestamp` DATETIME,
  `timestamp` DATETIME NOT NULL,
  PRIMARY KEY (`notification_id`));