ormar/docs/queries/aggregations.md

Aggregation functions

Currently 2 aggregation functions are supported.

• count() -> int

• exists() -> bool

• QuerysetProxy

  • QuerysetProxy.count() method
  • QuerysetProxy.exists() method

count

count() -> int

Returns number of rows matching the given criteria (i.e. applied with filter and exclude)

class Book(ormar.Model):
    class Meta:
        tablename = "books"
        metadata = metadata
        database = database

    id: int = ormar.Integer(primary_key=True)
    title: str = ormar.String(max_length=200)
    author: str = ormar.String(max_length=100)
    genre: str = ormar.String(
        max_length=100,
        default="Fiction",
        choices=["Fiction", "Adventure", "Historic", "Fantasy"],
    )

# returns count of rows in db for Books model
no_of_books = await Book.objects.count()

exists

exists() -> bool

Returns a bool value to confirm if there are rows matching the given criteria (applied with filter and exclude)

class Book(ormar.Model):
    class Meta:
        tablename = "books"
        metadata = metadata
        database = database

    id: int = ormar.Integer(primary_key=True)
    title: str = ormar.String(max_length=200)
    author: str = ormar.String(max_length=100)
    genre: str = ormar.String(
        max_length=100,
        default="Fiction",
        choices=["Fiction", "Adventure", "Historic", "Fantasy"],
    )

# returns a boolean value if given row exists
has_sample = await Book.objects.filter(title='Sample').exists()

QuerysetProxy methods

When access directly the related ManyToMany field as well as ReverseForeignKey returns the list of related models.

But at the same time it exposes a subset of QuerySet API, so you can filter, create, select related etc related models directly from parent model.

count

Works exactly the same as count function above but allows you to select columns from related objects from other side of the relation.

!!!tip To read more about QuerysetProxy visit [querysetproxy][querysetproxy] section

exists

Works exactly the same as exists function above but allows you to select columns from related objects from other side of the relation.

!!!tip To read more about QuerysetProxy visit [querysetproxy][querysetproxy] section