django models: how to select only objects which aren't belong to the inherited class?

I have two models in my Django 1.1.1 application:

class UserRequest(models.Model):
   # blah blah

class JournalistRequest(UserRequest):
    # blah blah

So, JournalistRequest is a special type of UserRequest, and all Journal开发者_如何学GoistRequests are still common UserRequests with special fields.

JournalistRequest.objects.all() returns all JournalistRequests. UserRequest.objects.all() returns all UserRequests, both Journalists and not. How to select all UserRequests which are not JournalistRequests?

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Assuming you are using multi-table inheritance, the following should work:

UserRequest.objects.filter(journalistrequest=None)