public static function execute( $sql, $parameters = null, $connection = null, $fetchMode = \PDO::FETCH_ASSOC )
    {
        self::$_statement = self::createStatement( $sql, $connection, $fetchMode );

        if ( empty( $parameters ) )
        {
            return self::$_statement->execute();
        }

        return self::$_statement->execute( $parameters );
    }