Detailed explanation of the method of implementing joint query in Symfony2

Acme\MspadminBundle\Entity\MspArticle:
 type: entity
 table: msp_article
 manyToOne:
  Channel:
   targetEntity: MspChannel
   inversedBy: Articles
   joinColumn:
    name: channel_id
    referencedColumnName: channel_id
  User:
   targetEntity: MspUser
   inversedBy: Userone
   joinColumn:
    name: user_id
    referencedColumnName: user_id

Acme\MspadminBundle\Entity\MspChannel:
 type: entity
 table: msp_channel
 oneToMany:
   Articles:
    targetEntity: MspArticle
    mappedBy: Channel

Acme\MspadminBundle\Entity\MspUser:
 type: entity
 table: msp_user
 oneToMany:
   Userone:
    targetEntity: MspArticle
    mappedBy: User

$sql="SELECT a.id,a.checkStatus,a.title,a.releaseSysDate,
          a.visitTotal,u.userName ,n.name FROM AcmeMspadminBundle:MspArticle a
          JOIN a.User u JOIN a.Channel n";
$query = $emt->createQuery($sql." Where a.checkStatus = 0 ");
$mspArtile = $query->getResult();