looping through an array problem

This is something dumb I am doing but: Trying to pull all names of publishers in db. This sql: SELECT art.art_id,art.publisher_id,publisher.publisher_name, FROM art LEFT JOIN publisher ON publisher.publisher_id=art.publisher_id pulls (in phpmyadmin) four rows:

  artID  pubID     Publisher_name
  1        7       The New York Times: Sunday Styles
  2        3       The New York Sun
  3        2       Metro NY
  4        3       The New York Sun

I'm trying to make a sidebar which will make links to each unique publisher name: while ($cartoon = mysql_fetch_assoc($result)) {

     $pub_sidebar[] = "<ul class='sidebar-menu'><a class='img-link' href='{$_SERVER['PHP_SELF']}?p={$cartoon['publisher_id']}' title=\"{$cartoon['publisher_name']}\">{$cartoon['publisher_name']}</a></ul>";

} This prints:

      The New York Times: Sunday Styles

      The New York Sun

      Metro NY

      The New York Sun

I'd like to stop the NY Sun from appearing twice! What have i missed here? Thanks in advance!