create table certificates (
  user_row_id int not null unique,
  first_name varchar(40) not null,
  last_name varchar(50) not null,
  email varchar(50) not null,
  birth_date date not null,
  test_datetime datetime not null,

  CONSTRAINT `fk_user_row_id` -- create fk constraint
  foreign key (user_row_id) references users (id) -- define constraint
  on update restrict -- define when the restriction should apply
);