protected function addJoin(
        string $table,
        string $key,
        string $operator,
        string $value,
        string $type = 'inner'
    ): void {
        array_push($this->join, [
            'table' => $table,
            'key' => $key,
            'operator' => $operator,
            'value' => $value,
            'type' => $type,
        ]);
    }