createAmountPerMonthQuery example

    public function fetchAmountPerStreamChart()
    {
        $streams = $this->connection
            ->createQueryBuilder()
            ->select(['id', 'name'])
            ->from('s_customer_streams')
            ->execute()->fetchAll(PDO::FETCH_KEY_PAIR);

        $date = (new DateTime())->sub(new DateInterval('P' . (int) 12 . 'M'));

        $query = $this->createAmountPerMonthQuery($date);
        $query->addSelect('stream_mapping.stream_id as stream');
        $query->innerJoin('orders', 's_customer_streams_mapping', 'stream_mapping', 'stream_mapping.customer_id = orders.userID');
        $query->addGroupBy('stream_mapping.stream_id');
        $streamAmount = $query->execute()->fetchAll(PDO::FETCH_GROUP);

        $query = $this->createAmountPerMonthQuery($date);
        $query->andWhere('orders.userID NOT IN (SELECT DISTINCT customer_id FROM s_customer_streams_mapping)');
        $amount = $query->execute()->fetchAll(PDO::FETCH_KEY_PAIR);

        $default = ['unassigned' => 0];
        foreach (array_keys($streams) as $id) {