Doctrine left join where joined table is null shows results - symfony

Question

the goal of this query is to show records from table orders that don't have any shipments created yet. Here is how it should be done in SQL:
SELECT *
FROM orders
LEFT JOIN orders_shipments shipments ON orders.trx_id = shipments.trx_id
WHERE shipments.shipment_id IS NULL
AND orders.purchase_date IS NOT NULL
AND orders.fulfillment_channel = 'MFN';
The following query shows 0 results. Vs the following:
$qb = $this->createQueryBuilder('orders');
$qb->select('orders, shipments')
->leftjoin('orders.shipments', 'shipments')
->Where('shipments.id IS NULL')
->ANDWhere('orders.purchaseDate IS NOT NULL')
->ANDWhere('orders.fulfillmentChannel = :a')->setParameter('a', 'MFN');;
$results = $qb->getQuery()
->getResult();
return $results;
Does show results. Why is that and how to fix it?

Answer 1

Not sure why but I had to use GROUP and HAVING to get it to work:
$qb = $this->createQueryBuilder('orders');
$qb->select('orders, shipments')
->leftjoin('orders.shipments', 'shipments')
->Where('shipments.id IS NULL')
->ANDWhere('orders.purchaseDate IS NOT NULL')
->ANDWhere('orders.fulfillmentChannel = :a')->setParameter('a', 'MFN')
->GroupBy('orders.id')
->having('count(shipments) = 0');
$results = $qb->getQuery()->getResult();