many-to-one (Foreign Key)
From Many (source of the relationship) to One (target)
Cardinality: many instances of source participate in the relationship with a single instance of destination
- Example: Many articles has one single reporter, but not in reverse
it’s suggested, but not required, that the name of a ForeignKey field (manufacturer in the example above) be the name of the model, lowercase.
many-to-many
Generally, ManyToManyField instances should go in the object that’s going to be edited on a form. In the above example, toppings is in Pizza (rather than Topping having a pizzas ManyToManyField ) because it’s more natural to think about a pizza having toppings than a topping being on multiple pizzas. The way it’s set up above, the Pizza form would let users select the toppings.
many-to-many with extra fields
one-to-one
- Example: Each Restaurant has only and only one specific Place, and each Place belongs sto only and only one specific Restaurant
one-to-many
Django doesn't explicitly define a One-to-Many relationship. However, it arises naturally from the Many-to-One relationship.
One-to-Many is implicit and accessed through the related manager, e.g., comment_set in the example of Blog and Comment relation
The related_name argument in the ForeignKey field can be used to customize the name of the related manager.