Question

I’m working with Symfony2.

I have an entity Employee and an entity Message related by an OneToMany association.

So a employee can have some messages and I want to have the one which has been sent the most recently, for a given employee.

Is this query correct ?

<?php
  public function getLast($id_employee)
  {
   $query = $this->_em->createQuery(
                 'SELECT MAX(m.sentAt) FROM MyBundle:Message m JOIN m.employee e 
                   WHERE e.id = ' . $id_employee);
    return $query->getSingleResult();
   }    

Thanks a lot

Answer 1

You haven’t need to do a JOIN since the external key is alredy onto your message table and since we can think that a message belongs only to one user and one user can have multiple messages related to him.

So your query will be

'SELECT MAX(m.sentAt), m.text 
 FROM MyBundle:Message m 
 WHERE m.employee_id = :id_employee'

and you have to modify your code in that way

$query = $this->_em->createQuery(
              'SELECT MAX(m.sentAt),m.text 
               FROM MyBundle:Message m 
               WHERE m.employee_id = :id_employee')
               ->setParameter('id_employee',$employee_id)
               return $query->getSingleResult();

However if you had to do a join, please remember this important things

1. If your entities are related with association and your only ON condition is about keys, you haven’t to specify it with WHERE clause
2. Doctrine provide you a “faster” method for do this type of query without using directly DQL (or use it only a little) and use something like ->leftJoin(..) , ->where(..) and so on