protected function getQueryItems()
    {
        /* this is primary query builder, not extender */
        $result = parent::getQueryItems();

        /* define tables aliases for internal usage (in this method) */
        $asDwnl = self::AS_DWNL;
        $asAcc = self::AS_ACCOUNT;

        /* LEFT JOIN prxgt_dwnl_customer */
        $tbl = $this->resource->getTableName(EDownline::ENTITY_NAME);
        $as = $asDwnl;
        $cols = [
            self::A_MLM_ID => EDownline::A_MLM_ID
        ];
        $cond = $as . '.' . EDownline::A_CUSTOMER_REF . '=' . $asAcc . '.' . EAccount::A_CUST_ID;
        $result->joinLeft([$as => $tbl], $cond, $cols);

        /* return  result */
        return $result;
    }