Sub query example

gistfile1.php

$subQuery = $this->getEntityManager()->createQueryBuilder();
$subQuery->select('relatedBallot.id')
    ->from('ProposalBundle:FloorModifiedProposal', 'floorModifiedProposal')
    ->join('floorModifiedProposal.ballotsRelatedToMe', 'relatedBallot')
    ->where($subQuery->expr()->eq('floorModifiedProposal.id', ':floorModifiedProposalId'));

$qb->andWhere($qb->expr()->notIn('fmps.id', $subQuery->getDQL()))
    ->setParameter('floorModifiedProposalId', $floorModifiedProposalId);