请教mysql_fetch_array问题出在那!

<?php
require_once ("./config/link.php");
mysql_select_db("nx00", $con);
$result = mysql_query("select * from nx00 order by id desc");
while($row = mysql_fetch_array($result))
  {
  echo $row['id'] . " " . $row['num'];
  echo "<br />";
  }
?>

link.php是数据库链接文件

Warning: mysql_fetch_array() expects parameter 1 to be resource, boolean given in /usr/local/www/apache22/data/twweb/find.php on line 8

$result = mysql_query("select * from nx00 order by id desc")
    or die("Invalid query: " . mysql_error());
echo $result;

看看什么提示。