public function select ($columns = self::DEFAULT_SELECT)
    {
        if (func_num_args() == 1)
        {
            $this->queryElements[self::SELECT_KEY] = (is_array($columns)) ? $this->formatAssociativeArray("%s AS %s", $columns) : array($columns);
        }
        else if (func_num_args() > 1)
        {
            $this->queryElements[self::SELECT_KEY] = func_get_args();
        }

        return $this;
    }