如何在查询中使用leftJoin和DISTINCT

Question

我正在尝试将SQL查询重写为Doctrine，但是DISTINCT选项存在很大问题。

SELECT DISTINCT airports_list.id, group_travel_airports.airport_id
FROM airports_list
LEFT JOIN group_travel_airports
    ON group_travel_airports.airport_id = airports_list.id AND
       group_travel_package_id = 109
WHERE group_travel_airports.airport_id IS NULL

我的代码：

$qb = $this->createQueryBuilder('g');
  $qb->select('DISTINCT a , g')
  ->leftJoin('App\Entity\AirportsList','a', Join::WITH , 'a = g.airport')
  ->where($qb->expr()->andx(
      $qb->expr()->isNotNull('g.airport'),
      $qb->expr()->eq('g.groupTravelPackage', $id)
   ));

您能显示一下外观吗？