Primary key behavior in Django - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a primary key in Django models?

A primary key is a unique identifier for each record in a database table. In Django, it uniquely identifies each model instance.

beginner

What happens if you don't define a primary key in a Django model?

Django automatically adds an id field as an auto-incrementing primary key.

intermediate

Can you use a field other than id as a primary key in Django?

Yes, you can set any field as the primary key by adding primary_key=True to that field.

intermediate

What is the behavior of a primary key field with primary_key=True in Django?

It becomes unique, non-nullable, and automatically used as the identifier for model instances.

beginner

Why should a primary key be unique and non-null in Django models?

Because it identifies each record uniquely and must always have a value to avoid confusion in data retrieval.

What does Django do if no primary key is defined in a model?

A Throws an error

B Adds an auto-incrementing <code>id</code> field as primary key

C Uses the first field as primary key

D Creates a composite key automatically

Django automatically adds an id field as the primary key if none is defined.

Which of these is true about a primary key field in Django?

A It must be unique

B It can be null

C It can have duplicate values

D It is optional

Primary keys must be unique and non-null to identify records uniquely.

How do you set a custom field as a primary key in Django?

A Add <code>unique=True</code> to the field

B Set <code>auto_increment=True</code>

C Add <code>primary_key=True</code> to the field

D Rename the field to <code>id</code>

Setting primary_key=True on a field makes it the primary key.

What type of field does Django use by default for the primary key?

A BooleanField

B CharField

C ForeignKey

D AutoField

Django uses an AutoField, an integer that auto-increments, as the default primary key.

Why is it important that a primary key is non-null?

A To ensure every record can be uniquely identified

B To speed up queries

C To allow multiple records with the same key

D To allow null values in other fields

A non-null primary key ensures each record is uniquely identifiable.

Explain what a primary key is in Django and how Django handles it if you don't define one.

Think about what Django adds automatically to every model.

Describe how to set a custom primary key in a Django model and what changes this causes.

Focus on the field attribute that changes primary key behavior.