title: Doctrine2 generates two extra tables for a ManyToMany relationship
body: <h1>Problem</h1>
  
  <p>I'm setting up a database by using Symfony2 and Doctrine2 (annotation). I followed the examples perfectly (<a href="http://docs.doctrine-project.org/en/2.0.x/reference/association-mapping.html#many-to-many-bidirectional" rel="noreferrer">Doctrine2 relationship documentation</a>), but somehow when I update my schema (<code>doctrine:schema:update --force</code>) it creates two additional tables.</p>
  
  <p>My two entities are Article and District, the code is below.</p>
  
  <h1>Code</h1>
  
  <h2>Article entity:</h2>
  
  <pre><code>/**
   *
   * @var \Doctrine\Common\Collections\ArrayCollection $districts
   *
   * @ORM\ManyToMany(targetEntity="District", inversedBy="articles")
   * @ORM\JoinTable(name="articles_districts",
   *     joinColumns={@ORM\JoinColumn(name="article_id", referencedColumnName="id")},
   *     inverseJoinColumns={@ORM\JoinColumn(name="district_id", referencedColumnName="id")}
   * )
   */
  protected $districts;
  </code></pre>
  
  <h2>District entity:</h2>
  
  <pre><code>/**
   *
   * @var \Doctrine\Common\Collections\ArrayCollection $articles
   * @ORM\ManyToMany(targetEntity="Article", inversedBy="districts")
   */
  protected $articles;
  </code></pre>
  
  <h1>Question</h1>
  
  <p>The two extra tables that are being created are: <code>articles_districts</code> (the one I specified in the JoinTable section) and <code>article_district</code> (the other one that somehow gets created automatically). </p>
  
  <p>The <code>articles_districts</code> table works as expected and ID's are inserted when a new entry is made. The <code>article_district</code> remains empty, and thus, is pretty useless. How do I get rid of it?</p>