title: How to add column in ManyToMany Table (Django)
body: <p>From the example of Django Book, I understand if I create models as following:</p>
  
  <pre><code>from xxx import B
  
  class A(models.Model):
      b = ManyToManyField(B)
  </code></pre>
  
  <p>The Django would create a new table(A_B) beyond Table A, which has three columns:</p>
  
  <ul>
  <li>id</li>
  <li>a_id</li>
  <li>b_id</li>
  </ul>
  
  <p>But now I want to add a new column in the Table A_B, thus would be very easy if I use normal SQL, but now anyone can help me how to do? I can't find any useful information in this book.</p>