mysql troubles

create table people (
  id int unsigned not null auto_increment unique,
  nick varchar(9) not null,
  first_seen datetime not null,
  primary key(nick)
) default charset=utf8 ENGINE=InnoDB;

create table url (
  id int unsigned not null auto_increment unique,
  url varchar(100) not null,
  nickid int unsigned not null,
  date datetime not null,
  constraint foreign key(nickid) references people(id),
  primary key(id)
) default charset=utf8 ENGINE=InnoDB;