Django ORM INNER JOIN SQL test

django_orm_inner_join.py

from django.db import models


class Banana(models.Model):
    name = models.CharField(max_length=255)
    father = models.ForeignKey('self', null=True)

    def __unicode__(self):
        return self.name

#>>> Banana.objects.all()
#[<Banana: John>, <Banana: Peter>, <Banana: Bob>]
#>>> Banana.objects.create(name="Chris", father=Banana.objects.all()[2])
#<Banana: Chris>
#>>> Banana.objects.filter(father__name="Bob")
#[<Banana: Chris>]

# Last ORM query does the following SQL:
# SELECT "main_banana"."id",
#        "main_banana"."name",
#        "main_banana"."father_id"
# FROM "main_banana" 
# INNER JOIN "main_banana" T2 ON ("main_banana"."father_id" = T2."id") WHERE T2."name" = Bob  LIMIT 21'

For anyone (new to Django) is interested in the self, here's the explanation:

# reference: https://books.agiliq.com/projects/django-orm-cookbook/en/latest/self_fk.html

class Employee(models.Model):
    manager = models.ForeignKey('self', on_delete=models.CASCADE)

# OR

class Employee(models.Model):
    manager = models.ForeignKey("app.Employee", on_delete=models.CASCADE)