ormar/docs/relations/many-to-many.md

ManyToMany

ManyToMany(to, through) has required parameters to and through that takes target and relation Model classes.

Sqlalchemy column and Type are automatically taken from target Model.

• Sqlalchemy column: class of a target Model primary key column
• Type (used for pydantic): type of a target Model

Defining Models

--8<-- "../docs_src/relations/docs002.py"

Create sample data:

guido = await Author.objects.create(first_name="Guido", last_name="Van Rossum")
post = await Post.objects.create(title="Hello, M2M", author=guido)
news = await Category.objects.create(name="News")

add

# Add a category to a post.
await post.categories.add(news)
# or from the other end:
await news.posts.add(post)

!!!warning In all not None cases the primary key value for related model has to exist in database.

Otherwise an IntegrityError will be raised by your database driver library.

remove

Removal of the related model one by one.

Removes also the relation in the database.

await news.posts.remove(post)

clear

Removal of all related models in one call.

Removes also the relation in the database.

await news.posts.clear()

QuerysetProxy

Reverse relation exposes QuerysetProxy API that allows you to query related model like you would issue a normal Query.

To read which methods of QuerySet are available read below querysetproxy