Django Order by field ignoring NULL

   Order_by is a commonly used django query to order the queryset based on the order_by field name. Basic syntax of order_by is shown below.

MyModel.objects.all().order_by('field_name')

Consider the following models.py

from django.db import models

class SelectedProducts(models.model):
    '''
    Model for storing the product basic updation details.
    '''
    name = models.CharField(max_length=250)
    price = models.FloatField(default=0.0)
    count = models.IntegerField(blank=True, null=True, max_length=5)

  def __unicode__(self):
       return self.name

Now consider the case where you have 3 entries in your table.

Name         Price           Count

abc              15.0               5
lmo            10.25              2
xyz             12.50           (None)

According to the following query:

     SelectedProducts.objects.all().order_by('count')

Output:
[ <objects:xyz>, <objects:lmo>, <objects:abc>]

Since the count of xyz is None, it will be shown first.
Now, to show model instance with count 'None' at the end, you can use following methods:

1. Method: Using 'extra'

Based on this method code will  be:

    selected = SelectedProducts.objects.all().order_by('count')
    q = selected.extra(select={'count_null': 'count is null'})
    q = q.extra(order_by=['count_null'])
    print q

Output:
[ <objects:lmo>, <objects:abc>, <objects:xyz>]

In some cases the above approach returns sql syntax error.

2. Method: Using 'aggregate'

Based on this method code will  be:

    from django.db.models import Count
    q = SelectedProducts.objects.all().annotate(null_count=Count('count')).order_by('-null_count', 'count')
    print q

Output:
[ <objects:lmo>, <objects:abc>, <objects:xyz>]