title: how to add a new field in django model
body: <p>this is my model :</p>
  
  <pre><code>class zjm_model(models.Model):
      a = models.CharField(max_length=36)
      b = models.CharField(max_length=36)
  </code></pre>
  
  <p>and the table <code>zjm_model</code> has many data in my mysql , and now ,</p>
  
  <p>i want to add a new field :</p>
  
  <pre><code>class zjm_model(models.Model):
      a = models.CharField(max_length=36)
      b = models.CharField(max_length=36)
      c = models.CharField(max_length=36)
  </code></pre>
  
  <p>but , when i run <code>manage.py syncdb</code> , it show this :</p>
  
  <pre><code>No fixtures found.
  </code></pre>
  
  <p>so  how can i to add a new field  to my database ,</p>
  
  <p>thanks</p>