title: Django filtering data from primary key relational tables
body: <p>I have a read-only MSSQL database which I successfully managed to read from using django.
  This database's got tables which are all primary-keyed and models are:</p>
  
  <pre><code>class City(models.Model):
      id = models.IntegerField(primary_key=True)
      name = models.CharField(max_length=20)
  
  class Neighborhood(models.Model):
      id = models.IntegerField(primary_key=True)
      name = models.CharField(max_length=20)
  
  class Person(models.Model):
      id = models.IntegerField(primary_key=True)
      fname = models.CharField(max_length=10)
      mname = models.CharField(max_length=10)
      lname = models.CharField(max_length=10)
      address = models.CharField(max_length=100)
      neighborhood = models.ForeignKey(Neighborhood)
      city = models.ForeignKey(City)
      phone = models.CharField(max_length=20)
      email = models.EmailField()
  </code></pre>
  
  <p>I wish to filter <code>Person</code> by supplying <code>Neighborhood</code> and/or <code>City</code>.
  Unfortunately I cannot alter tables or change db as it's read-only. How can it be done?
  Thanks </p>