问关于不相关实体的理论

EN

$qbt = $this->_em->createQueryBuilder();
$qbt
    ->select('conference', 'diffusion', 'speaker', 'placediff', 'confcity')
    ->from('AppBundle:Conference', 'conference')
    ->leftJoin('conference.diffusion', 'diffusion')
    ->leftJoin('conference.speaker','speaker')
    ->leftJoin('conference.place','placediff')
    ->leftJoin('AppBundle:City', 'confcity', 'WITH', 'confcity.id = placediff.city');

return $qbt
    ->getQuery()
    ->setHint(\Doctrine\ORM\Query::HINT_INCLUDE_META_COLUMNS, true)
    ->useQueryCache(true)
    ->useResultCache(true, 3600)
    ->getArrayResult();

    public function rawConf()
    {
        $conn = $this->getEntityManager()->getConnection();
        $sql = 'SELECT
  c0_.id AS id,
  c0_.startAt AS startat,
  c0_.comment AS comment,
  d1_.id AS diffusion_id,
  d1_.hour AS diffusion_hour,
  s2_.id AS speaker_id,
  c0_.place_id AS place_id,
  c0_.sponsor_id AS sponsor_id,
  c0_.tour_id AS tour_id_8,
  d1_.movie_id AS diffusion_movie_id,
  s2_.contact_id AS speaker_contact_id,
  c6_.name AS ville_name,
  c6_.postal AS ville_post,
  c6_.department as ville_depart
FROM
  conference c0_
  LEFT JOIN conference_diffusion c3_ ON c0_.id = c3_.conference_id
  LEFT JOIN diffusion d1_ ON d1_.id = c3_.diffusion_id
  LEFT JOIN conference_speaker c4_ ON c0_.id = c4_.conference_id
  LEFT JOIN speaker s2_ ON s2_.id = c4_.speaker_id
  LEFT JOIN place p5_ ON c0_.place_id = p5_.id
  LEFT JOIN city c6_ ON (c6_.id = p5_.city_id)';

        $stmt = $conn->prepare($sql);

        $stmt->execute();

        return $stmt->fetchAll();

    }