error in function _advanced_forum_get_last_topic

with a postgresql database, there is an error syntax : "AS" keyword is forgotten is the two "select" requests, causing errors.
Good function is as follow:

/*****************************************************************************/
/*** LAST UPDATED TOPIC ******************************************************/
/*****************************************************************************/
function _advanced_forum_get_last_topic($tid) {
  // Get the most recently created node, in the given forum, that the user has access to
  $query = "SELECT n.nid AS topic_id,
                   n.title AS topic_title, 
                   n.created AS topic_timestamp,
                   n.type AS topic_type,
                   n.uid AS topic_author_id,
                   u.name AS topic_author_name
            FROM {node} n
            INNER JOIN {term_node} tn on n.nid = tn.nid
            INNER JOIN {users} u on n.uid = u.uid
            WHERE tn.tid = $tid AND n.status = 1
            ORDER BY n.created DESC";
            
  $node = db_fetch_object(db_query_range(db_rewrite_sql($query), array(), 0, 1));

  // If there is at least one node, then we need to look for the most recent comment       
  if ($node) {
    $query = "SELECT c.nid AS topic_id, 
                     c.cid AS reply_id,
                     c.timestamp AS reply_timestamp,
                     c.subject AS reply_title,
                     c.uid AS topic_author_id,
                     n.title AS topic_title, 
                     n.created AS topic_timestamp,
                     n.type AS topic_type,     
                     c.name AS reply_author_name           
              FROM {comments} c
              INNER JOIN {term_node} tn ON c.nid = tn.nid
              INNER JOIN {node} n ON c.nid = n.nid
              WHERE tn.tid = $tid AND n.status = 1 AND c.status = 0
              ORDER BY c.timestamp DESC";

    $comment = db_fetch_object(db_query_range(db_rewrite_sql($query,'c','cid'), array(), 0, 1));

    if ($node->topic_timestamp >= $comment->reply_timestamp) {
      $node->tid = $tid;
      $node->reply_id = 0;
      return $node;
    }
    else {
      $comment->tid = $tid;
      return $comment;
    }  
  }
}