title: Is it possible to have more than one foreign key in a normalised database schema?
body: <blockquote>
    <p>Address (<strong>addressID</strong>, houseNumber, postcode, roadName, city, county)<br>
    Reservation (<strong>reservationID</strong>, roomNo, <em>leadGuestID, guest2ID, guest3ID</em>,<br>
    &nbsp;arrivalDate, departureDate, <em>addressID</em>, amountOutstanding)<br>
    Guest (<strong>guestID</strong>, firstName, lastName, adultFlag, telephoneNo, <em>addressID</em>, emailAddress)<br>
    Room (<strong>roomNo</strong>, <em>roomTypeName</em>)<br>
    RoomType (<strong>roomTypeName</strong>, floor, basePrice, extraAdultPrice, extraChildPrice)  </p>
  </blockquote>
  
  <p>The above schema is supposed to be normalised 4NF. But I cannot see how <em>leadGuestID, guest2ID &amp; guest3ID</em> can be foreign keys, since they do not exist as primary keys in any other table. There are probably other issues here as well.</p>