public function fetchOne($query, $parameters = null)
{
if ($query instanceof ResultSet) {
$resultSet = $query;
} else {
$resultSet = new ResultSet();
$resultSet->initialize($this->execute($query, $parameters));
}
$result = $resultSet->getDataSource()->getResource()->fetchColumn();
$resultSet->getDataSource()->getResource()->closeCursor();
return $result;
}