public function getGroupByString($includeText = true)
    {
        $statement = "";

        foreach ($this->groupBy as $groupBy) {
            $statement .= $groupBy['column'];

            if ($groupBy['order']) {
                $statement .= " " . $groupBy['order'];
            }

            $statement .= ", ";
        }

        $statement = substr($statement, 0, -2);

        if ($includeText && $statement) {
            $statement = "GROUP BY " . $statement;
        }

        return $statement;
    }