How to have a Django relational database with four tables?

Question

I am creating a website using Django and have a problem with the database! I have four tables (topics, questions, answers, and images). Each one of these tables has an id column and I would like to connect these four tables together.

I have tried to use a ForeignKey() but that didn't work out. I am receiving an error message. I don't know if I can use ManyToManyField() in this case, because it is only one column that I am trying to connect.

This is the code:

from django.db import models

# Create your models here.
class topics(models.Model):
    topic_id = models.AutoField(primary_key=True)
    topic_level = models.BooleanField()
    topic_name = models.TextField()

class questions(models.Model):
    question_id = models.AutoField(primary_key=True)
    description = models.TextField()
    questions_type = models.BooleanField()


class answers(models.Model):
    answer_id = models.AutoField(primary_key=True)
    description = models.TextField()

class images (models.Model):
    image_id = models.AutoField(primary_key=True)
    image_blob = models.BinaryField()

This is the code with the ForeignKey():

from django.db import models

# Create your models here.
class topics(models.Model):
    topic_id = models.AutoField(primary_key=True)
    topic_level = models.BooleanField()
    topic_name = models.TextField()
    topic_question = models.ForeignKey(questions, on_delete=CASCADE)
    topic_answer = models.ForeignKey(answers, on_delete=CASCADE)
    topic_image = models.ForeignKey(images, on_delete=CASCADE)


class questions(models.Model):
    question_id = models.AutoField(primary_key=True)
    description = models.TextField()
    questions_type = models.BooleanField()
    question_topic = models.ForeignKey(topics, on_delete=CASCADE)
    question_answer = models.ForeignKey(answers, on_delete=CASCADE)
    question_image = models.ForeignKey(images, on_delete=CASCADE)


class answers(models.Model):
    answer_id = models.AutoField(primary_key=True)
    description = models.TextField()
    answer_topic = models.ForeignKey(topics, on_delete=CASCADE)
    answer_question = models.ForeignKey(questions, on_delete=CASCADE)
    answer_image = models.ForeignKey(images, on_delete=CASCADE)

class images (models.Model):
    image_id = models.AutoField(primary_key=True)
    image_blob = models.BinaryField()
    image_topic = models.ForeignKey(topics, on_delete=CASCADE)
    image_question = models.ForeignKey(questions, on_delete=CASCADE)
    image_answer= models.ForeignKey(answers, on_delete=CASCADE)

And this is the error message that I am receiving:

topic_question = models.ForeignKey(questions, on_delete=CASCADE) NameError: name 'questions' is not defined

Answer 1

At the point you're trying to use the question class name for indicating the related model, such class is not defined, as the error states. When you're referencing a model that is defined later in the code you must enclose the name in "":

topic_question = models.ForeignKey("questions", on_delete=CASCADE)

Here is the related docs: https://docs.djangoproject.com/en/dev/ref/models/fields/#django.db.models.ForeignKey