getPriceGroupDiscountFields example

 {
        $this->connection = $connection;
        $this->priceHydrator = $priceHydrator;
        $this->fieldHelper = $fieldHelper;
    }

    public function getPriceGroups(Group $customerGroup, ShopContextInterface $context)
    {
        $query = $this->connection->createQueryBuilder();

        $query->addSelect('priceGroupDiscount.groupID')
            ->addSelect($this->fieldHelper->getPriceGroupDiscountFields())
            ->addSelect($this->fieldHelper->getPriceGroupFields());

        $query->from('s_core_pricegroups_discounts', 'priceGroupDiscount')
            ->innerJoin('priceGroupDiscount', 's_core_pricegroups', 'priceGroup', 'priceGroup.id = priceGroupDiscount.groupID')
            ->andWhere('priceGroupDiscount.customergroupID = :customerGroup')
            ->groupBy('priceGroupDiscount.id')
            ->orderBy('priceGroupDiscount.groupID')
            ->addOrderBy('priceGroupDiscount.discountstart')
            ->setParameter(':customerGroup', $customerGroup->getId());

        $data = $query->execute()->fetchAll(PDO::FETCH_GROUP);