Symfony2.4 Doctrine从实体表以外的表中提取属性

Let's say I have object A.

/**
 * @Table(name="a")
 * repo class definition annotation here
 **/

class A {
   /**
    * @Column(name="id")
    * ... etc
    **/
   private $id; 

   /**
    * this is pulled from another table. It is not an entity, just a    decimal value
    */ 
   private $otherThingFromAnotherTable;
}

How can I pull $otherThingFromAnotherTable from table other_table using ORM annotations? It's not an entity, it's just a decimal value.

I've got the following annotations, so far:

* @ORM\OneToOne(targetEntity="??")
* @ORM\JoinTable(name="other_table",
*            joinColumns={
*                @ORM\JoinColumn(name="offer_id", referencedColumnName="id")
*            }
* )

Currently, I am just using raw queries in the repo class so I can use it through the entity manager. Unfortunately, that only returns an array, not the object. I'd like to be able to use just $this->em->repo->find($id) and have it pull everything automatically instead of a custom method.