Magento : Set Random Order in Collection

we can select random rows from MySQL table using Zend_Db_Expr(‘RAND()’),
here we have to create a new function in module collection class
(Namespace/Module/Model/Mysql4/Module/Collection.php)
public function setRandomOrder()
{
    $this->getSelect()->order(new Zend_Db_Expr('RAND()'));
    return $this;
}
And use it as
$collection = Mage::getModel('test/test')
                    ->getCollection()
                    ->setRandomOrder();