Joomla output SQL query

some_joomla_extension.php

<?php
// Usage 
echo $db->replacePrefix((string) $query) ;

// Example
    $db = JFactory::getDbo();
		$query = $db->getQuery(true);
		$query->select( 'id' );
		$query->from($db->quoteName('#__kunena_categories'));
		$query->where($db->quoteName('parent_id')  . '=' . $db->quote( $parent_id ));
		$query->where($db->quoteName('name')  . '=' . $db->quote( $title ));

		$db->setQuery($query);
    echo $db->replacePrefix((string) $query) ;
		$result = $db->loadResult();;