// Get all modDocuments (resources) with template id 2 (2 = 'Service')

// This does not work
$query = $modx->newQuery('modResource');
$query->leftJoin('modTemplate', 'template');
$query->where(array(
    'template.templatename' => 'Service'
));
$query->sortby('pagetitle', 'ASC');

// This does work
$query = $modx->newQuery('modResource');
$query->where(array(
    'template' => 2
));
$query->sortby('pagetitle', 'ASC');