title: Django Models: I want to link a specific attribute of a model to another model that is not the primary key. How would I do it?
body: <p>I am relatively new with Django, and I need some help with my models.</p>
  
  <p>My models.py for the paperAssign app looks like (excluding all the imports):</p>
  
  <pre><code>class Reviewer(models.Model):
  
      reviewerID = models.AutoField(primary_key=True)
      paper = models.ManyToManyField(Document)
  
      Select_Reviewer = models.OneToOneField(RegUser, default=None)
  
      def __str__(self):
          return "%s" % (self.Select_Reviewer)
  </code></pre>
  
  <p>and my models.py file for the review app looks like (excluding all the imports):</p>
  
  <pre><code>SCORE_CHOICES = (
      (1, '1'),
      (2, '2'),
      (3, '3'),
      (4, '4'),
      (5, '5'),
      (6, '6'),
      (7, '7'),
      (8, '8'),
      (9, '9'),
      (10, '10'),
  )
  
  CONFIDENCE_CHOICES = (
      (1, 'Not confident'),
      (2, 'Unsure'),
      (3, 'Somewhat confident'),
      (4, 'Moderately confident'),
      (5, 'Very confident'),
  )
  
  
  class Review(models.Model):
      comment = models.TextField()
      score = models.IntegerField(choices=SCORE_CHOICES)  
      confidence = models.IntegerField(choices=CONFIDENCE_CHOICES)
      paper = models.ForeignKey(Document)
  
      def __str__(self):
          return '%s' % (self.paper)
  </code></pre>
  
  <p>I need to connect the <code>paper</code> attribute of class <code>Review</code> to the <code>paper</code> attribute of class <code>Reviewer</code>. Is it possible to have a second primary key? Or how should I do this?</p>
  
  <p>Thank you in advance! </p>