Netestované:

$dotaz = mysql_query("SELECT `tb-id` FROM `menu` ORDER BY 1");
$a = 1;
while ($b = mysql_fetch_assoc($dotaz)) {
  $b = (int)$b['tb-id'];
  while ($a < $b) {
    echo '<option value="' . $a . '">' . $a . '</option>';
    $a++;
  }
  $a++
}
while ($a <= 100) {
  echo '<option value="' . $a . '">' . $a . '</option>';
  $a++;
}