How to do custom query in magento?

I want to write a custom query in magento website.

I created a file test.php in my magento root folder & written a custom query

<?php
 $read= Mage::getSingleton('core/resource')->getConnection('core_read');
 $value=$read->query("Select * from catalog_product_flat_1");
 $row = $value->fetch();
 echo "<pre>";print_r($row);echo "</pre>";
?>

But it is not giving me any results.Please guide me.