AL
<?php
$res = $modx->db->query('Select id,pagetitle from '.$modx->getFullTableName('site_content').' where alias=""');
while ($row = $modx->db->getRow($res))
{
$alias = $modx->stripAlias($row['pagetitle']);
$modx->db->query('Update '.$modx->getFullTableName('site_content').' set alias="'.$alias.'" where id='.$row['id']);
}
echo 'complete!';