Django model with two foreign keys

Question

I have the following models in django and I want to get in a queryset the customers of a specific salesman. That means that I want the customers that have at least one policy with a specific salesman.

class Salesman(models.Model):
      name = models.Charfield()

class Customer(models.Model):
      name = models.Charfield()

 class Policy(models.Model):
      policy_number = models.Charfield()
      salesman = models.Foreignkey(Salesman)
      customer = models.Foreignkey(Customer)

Can anyone help?

Answer 1

You can follow the foreign key backwards from customer to policy. Then use the double underscore to filter the salesman.

salesman = Salesman.objects.get(name="Loman")
Customer.objects.filter(policy__salesman=salesman).distinct()

The distinct() is required to prevent duplicates if the customer has more than one policy with that salesman.

See the docs on lookups that span relationships for more info.