text: ALTER TABLE cans ADD deleted_at TIMESTAMP NULL;
  ALTER TABLE cans ADD identifier VARCHAR(50) NOT NULL UNIQUE AFTER id;
  
  
  CREATE TABLE can_data (
      id              INT UNSIGNED NOT NULL  AUTO_INCREMENT,
      can_id          INT UNSIGNED NOT NULL,
      moment   TIMESTAMP NOT NULL DEFAULT NOW(),
      filling_rate    DOUBLE(5,3) NOT NULL,
  
      PRIMARY KEY (id),
      FOREIGN KEY (can_id) REFERENCES cans (id)
  );