Doctrine Dql for One-To-Many, Unidirectional with Join Table - doctrine-orm

Question

So I've read the following article.
I've done something similar with my own entities and am trying to create a DQL.
DQL:
$em = $this->getDoctrine()->getManager();
$query = $em->createQuery(
'SELECT s,st,tt
FROM CrmClientBundle:Session s
INNER JOIN s.session_treatments st
INNER JOIN st.treatment_type_id tt
WHERE s.client_id = ' . $id
);
$sessions = $query->getResult();
I receive the following error though:
[Semantical Error] line 0, col 152 near 'tt
': Error: Class Crm\ClientBundle\Entity\TreatmentType has no association named
treatment_type_id
However if I remove the second join and check the symfony profiler it creates the following query which seems to me that I have created my entities properly:
SELECT
s0_.id AS id0,
s0_.client_id AS client_id1,
s0_.date AS date2,
s0_.session_id AS session_id3,
s0_.session_type AS session_type4,
s0_.session_cost AS session_cost5,
s0_.products_bought AS products_bought6,
s0_.products_cost AS products_cost7,
s0_.total_cost AS total_cost8,
s0_.total_paid AS total_paid9,
s0_.notes AS notes10,
t1_.id AS id11,
t1_.type AS type12,
t1_.cost AS cost13,
t1_.category_id AS category_id14
FROM
sessions s0_
INNER JOIN session_treatments s2_ ON s0_.id = s2_.session_id
INNER JOIN treatment_types t1_ ON t1_.id = s2_.treatment_type_id
WHERE
s0_.client_id = 1
Crm\ClientBundle\Session.php:
/**
* #ORM\Entity
* #ORM\Table(name="sessions")
*/
class Session {
/**
* #ORM\Id
* #ORM\Column(type="integer")
* #ORM\GeneratedValue(strategy="AUTO")
*/
private $id;
/** #ORM\Column(type="integer") */
private $client_id;
/** #ORM\Column(type="date") */
private $date;
/**
* **
* #ORM\ManyToMany(targetEntity="TreatmentType")
* #ORM\JoinTable(name="session_treatments",
* joinColumns={#ORM\JoinColumn(name="session_id", referencedColumnName="id")},
* inverseJoinColumns={#ORM\JoinColumn(name="treatment_type_id", referencedColumnName="id ", unique=true)}
* )
*/
private $session_treatments;
/**
* Constructor
*/
public function __construct()
{
$this->session_treatments = new ArrayCollection();
}
}
Crm\ClientBundle\TreatmentType.php:
/**
* #ORM\Entity
* #ORM\Table(name="treatment_types")
*/
class TreatmentType {
/**
* #ORM\Id
* #ORM\Column(type="integer")
* #ORM\GeneratedValue(strategy="AUTO")
*/
private $id;
/** #ORM\Column(type="string", length=255) */
private $type;
/** #ORM\Column(type="decimal") */
private $cost;
}

Answer 1

You have 2 entities and you are trying to retrieve 3 entities. The second join is unnecessary. It's only needed if TreatmentType has yet another relationship (other then the one with Session). For clarification:
$em = $this->getDoctrine()->getManager();
$query = $em->createQuery(
'SELECT s,st,tt
FROM CrmClientBundle:Session s // <-- s is your Session
INNER JOIN s.session_treatments st // <-- st is your TreatmentType
INNER JOIN st.treatment_type_id tt <-- TreatmentType does not have a property $treatement_type_id that points to non-defined relationship. tt would be your 3rd entity.
WHERE s.client_id = ?1'
);
$query->setParameter(1, $id);
$sessions = $query->getResult();
Bonus: used bound a parameter -- helps against SQL injection and speeding up your query in the future