query.php

<?php
$query = DB::insert('users_roles', array('user_id', 'role_id'))
	->values(array($this->id, DB::expr("(".
		DB::select('id')
			->from('roles')
			->where('name', '=', $rolename))
		.")"));

echo $query
?>

-->

INSERT INTO `users_roles` (`user_id`, `role_id`) VALUES (3, '(SELECT `id` FROM `roles` WHERE `name` = \'login\')')