OneToOneField for one-to-one in Django - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a OneToOneField in Django?

A OneToOneField creates a one-to-one relationship between two models, meaning each record in one model is linked to exactly one record in another model.

beginner

How do you define a one-to-one relationship in Django models?

Use models.OneToOneField inside a model to link it to another model with a one-to-one relationship.

beginner

What is a real-life example of a one-to-one relationship?

A person and their passport: each person has exactly one passport, and each passport belongs to exactly one person.

intermediate

What happens if you try to create two records linked to the same record using a OneToOneField?

Django will raise an IntegrityError because OneToOneField enforces uniqueness, so only one record can link to the other.

intermediate

How do you access the related object in a one-to-one relationship?

You can access the related object using the attribute name defined by the OneToOneField on the model instance.

What does OneToOneField enforce between two Django models?

A No relationship between models

B Multiple records in one model can link to one record in the other

C One record links to many records in the other model

D Each record in one model links to exactly one record in the other model

OneToOneField ensures a strict one-to-one link between two models.

Which Django field type would you use to create a one-to-one relationship?

A models.ManyToManyField

B models.ForeignKey

C models.OneToOneField

D models.CharField

models.OneToOneField is the correct field for one-to-one relationships.

If a OneToOneField is set on model A pointing to model B, how do you access model B from an instance of model A?

A Using the attribute name of the <code>OneToOneField</code>

B Using a query on model B

C Using a list of related objects

D You cannot access model B from model A

The related object is accessed directly via the attribute defined by the OneToOneField.

What error occurs if you try to link two records to the same record using a OneToOneField?

A ValueError

B IntegrityError

C TypeError

D No error

Django raises an IntegrityError because the uniqueness constraint is violated.

Which of these is a good example of a one-to-one relationship?

A A student and their ID card

B A book and its author

C A teacher and their students

D A blog post and its comments

Each student has exactly one ID card, and each ID card belongs to one student.

Explain how to create and use a OneToOneField in Django models.

Think about how two models can be connected so each record matches exactly one record in the other.

Describe a real-life situation where a one-to-one relationship fits well and how it maps to Django models.

Think about unique pairs in everyday life.