TYPO3 DBAL Querybuilder: Cross-database join

Question

I want to write a select query to an existing database structure:

    private function select(): QueryBuilder
    {
        return ($queryBuilder = $this->connectionPool->getQueryBuilderForTable('deployment'))
            ->select('deployment.*', 'address.*', 'lpt_address.*')
            ->from('deployment')
            ->leftJoin(
                'deployment',
                'address',
                'address',
                $queryBuilder->expr()->eq('address.id', $queryBuilder->quoteIdentifier('deployment.address'))
            )
            ->leftJoin(
                'deployment',
                'address',
                'lpt_address',
                $queryBuilder->expr()->eq('lpt_address.id', $queryBuilder->quoteIdentifier('deployment.lpt_address'))
            );
    }

The problem is, that the tables deployment and address are in different databases. How can I tell DBAL that address is in database mdb rather than hwdb?