django foreign key ondelete

1. How do I reference a foreign key in Django?
2. Can a foreign key be null in Django?
3. How do I delete a foreign key in Django?
4. What is a foreign key in Django?
5. What is primary key in Django model?
6. How does Django implement one to many relationship?
7. Can foreign key be null?
8. What is AutoField in Django?
9. IS NOT NULL in Django?
10. What does On_delete mean Django?
11. WHAT IS models protect in Django?
12. What is related name Django?

How do I reference a foreign key in Django?

Related objects reference

1. The “other side” of a ForeignKey relation. That is: from django.db import models class Blog(models. Model): # ... pass class Entry(models. Model): blog = models. ...
2. Both sides of a ManyToManyField relation: class Topping(models. Model): # ... pass class Pizza(models. Model): toppings = models. ManyToManyField(Topping)

Can a foreign key be null in Django?

ForeignKey does not allow null values.

How do I delete a foreign key in Django?

A better way to do this and that works with object's delete method and queryset's delete method is using the post_delete signal, as you can see in the documentation. You can override the delete() method of the Profile class and delete the other objects in this method before you delete the actual profile.

What is a foreign key in Django?

ForeignKey is a Django ORM field-to-column mapping for creating and working with relationships between tables in relational databases. ForeignKey is defined within the django. db. models. related module but is typically referenced from django.

What is primary key in Django model?

By default, Django adds an id field to each model, which is used as the primary key for that model. You can create your own primary key field by adding the keyword arg primary_key=True to a field. If you add your own primary key field, the automatic one will not be added.

How does Django implement one to many relationship?

To handle One-To-Many relationships in Django you need to use ForeignKey . The current structure in your example allows each Dude to have one number, and each number to belong to multiple Dudes (same with Business).

Can foreign key be null?

Short answer: Yes, it can be NULL or duplicate. I want to explain why a foreign key might need to be null or might need to be unique or not unique. First remember a Foreign key simply requires that the value in that field must exist first in a different table (the parent table). ... Null by definition is not a value.

What is AutoField in Django?

AutoField is a Django ORM mapping from your Python code to an integer-type column in your relational database. The Django project has great documentation for AutoField as well as all of the other column fields.

IS NOT NULL in Django?

The Django convention is to use the empty string, not NULL. The default values of null and blank are False. Also there is a special case, when you need to accept NULL values for a BooleanField , use NullBooleanField instead.

What does On_delete mean Django?

The on_delete method is used to tell Django what to do with model instances that depend on the model instance you delete. (e.g. a ForeignKey relationship). The on_delete=models. CASCADE tells Django to cascade the deleting effect i.e. continue deleting the dependent models as well. Here's a more concrete example.

WHAT IS models protect in Django?

PROTECT. The PROTECT argument of the ForeignKey on_delete option prevents the referenced object from being deleted if it already has an object referencing it in the database. Put simply, Django will prevent a post from deletion if it already has comments.

What is related name Django?

The related_name attribute specifies the name of the reverse relation from the User model back to your model. If you don't specify a related_name , Django automatically creates one using the name of your model with the suffix _set , for instance User. ... The Django documentation has more details.