title: django sync db question
body: <p>In django models say this model exist in details/models.py</p>
  
  <pre><code>    class OccDetails(models.Model):
         title = models.CharField(max_length = 255)
         occ = models.ForeignKey(Occ)
  </code></pre>
  
  <p>So when sync db is made the following fields get created </p>
  
  <p>and later to this of two more fields are added and sync db is made the new fields doesnt get created.How is this to be solved,Also what is auto_now=true in the below</p>
  
  <p>these are the new fields</p>
  
  <pre><code>         created_date = models.DateTimeField(auto_now_add=True)
           modified_date = models.DateTimeField(auto_now_add=True, auto_now=True)
  </code></pre>