Sure, you can use the session key of Django as a foreign key by creating a new model that inherits from the django.contrib.sessions.models.Session model and adding a foreign key to the user model.

The following code shows how to do this:

Python

from django.contrib.sessions.models import Session
from django.db import models

class SessionUser(models.Model):
    session_key = models.ForeignKey(Session, on_delete=models.CASCADE)
    user = models.ForeignKey('auth.User', on_delete=models.CASCADE)

This code creates a new model called SessionUser that inherits from the django.contrib.sessions.models.Session model. The session_key field is a foreign key to the Session model, and the user field is a foreign key to the auth.User model.

To use the session_key field as a foreign key, you would need to create a new model that inherits from the SessionUser model. For example, the following code shows how to create a new model called Order that inherits from the SessionUser model:

Python

from django.db import models

class Order(SessionUser):
    order_number = models.CharField(malength=100)
    total_price = models.DecimalField(madigits=10, decimal_places=2)

This code creates a new model called Order that inherits from the SessionUser model. The order_number field is a string field that stores the order number, and the total_price field is a decimal field that stores the total price of the order.

You can then use the session_key field to query the Order model. For example, the following code shows how to query the Order model for all orders that were placed by the user with the session key 1234567890:

Python

from django.db.models import Q

orders = Order.objects.filter(session_key=1234567890)

This code will return a list of all orders that were placed by the user with the session key 1234567890.