Topic guide Aggregation

Fields that are mentioned in the order_by() part of a queryset are used when selecting the output data, even if they are not otherwise specified in the values() call.

Topic guide Database access optimization

To make use of the caching behavior of QuerySet, you may need to use the with template tag.

Topic guide Making queries

Keyword argument queries – in filter(), etc. – are “AND”ed together. If you need to execute more complex queries (for example, queries with OR statements), you can use Q() objects.

Index

… lookup type - query() (Client method) - query_pk_and_slug (django.views.generic.detail.SingleObjectMixin attribute) - query_string (django.views.generic.base.RedirectView attribute) - QueryDict (class in django.http) - queryset | - QuerySet (class in django.db.models.query) - queryset (django.views.generic.detail.SingleObjectMixin attribute) - (django.views.generic.list.MultipleObjectMixin attribute) - (ModelChoiceField attribute) - (ModelMultipleChoiceField attribute) …

Internals Django Deprecation Timeline

Calling QuerySet.values_list() with flat=True and no field name will raise TypeError. The use of None when querying a JSONField top-level value will compile to SQL IS NULL. Use JSONNull to query for a JSON null value instead.

Reference Settings

Default: False Set this to True if you want to disable the use of server-side cursors with QuerySet.iterator(). Transaction pooling and server-side cursors describes the use case. This is a PostgreSQL-specific setting.

Topic guide Aggregation

Ordinarily, annotations are generated on a per-object basis - an annotated QuerySet will return one result for each object in the original QuerySet.

Topic guide

Article.objects.filter(publications__title__startswith="Science").distinct() <QuerySet [<Article: NASA uses Python>]> Reverse m2m queries are supported (i.e., starting at the table that doesn’t have a ManyToManyField): Excluding a related item works as you would expect, too (although the SQL involved is a little complex): If …

Topic guide Database access optimization

When you have a lot of objects, the caching behavior of the QuerySet can cause a large amount of memory to be used. In this case, iterator() may help.

Topic guide Making queries

To retrieve objects from your database, construct a QuerySet via a Manager on your model class. A QuerySet represents a collection of objects from your database. It can have zero, one or many filters.

Topic guide Making queries

Sometimes you want to set a field to a particular value for all the objects in a QuerySet. You can do this with the update() method. For example: You can only set non-relation fields and ForeignKey fields using this method.

How-to

Django offers a wide variety of built-in lookups for filtering (for example, exact and icontains). This documentation explains how to write custom lookups and how to alter the working of existing lookups.

Index

… | | --- | --- | | - A (class in django.contrib.gis.measure) - aadd() (RelatedManager method) - aaggregate() (in module django.db.models.query.QuerySet) - aauthenticate() (in module django.contrib.auth) - (ModelBackend method) - (RemoteUserBackend method) - Abs (class in django.db.models.functions) - ABSOLUTE_URL_OVERRIDES - …

Index

| | | | --- | --- | | - each_context() (AdminSite method) - earliest() (in module django.db.models.query.QuerySet) - editable (Field attribute) - ELLIPSIS (Paginator attribute) - ellipsoid (SpatialReference attribute) - email (models.User attribute) - EMAIL_BACKEND - setting - EMAIL_FIELD …

Index

… - import_wkt() (SpatialReference method) - import_xml() (SpatialReference method) - ImproperlyConfigured - in - field lookup type - in_bulk() (in module django.db.models.query.QuerySet) - include - template tag - include (ExclusionConstraint attribute) - (Index attribute) - (UniqueConstraint attribute) - include() (in module …

Internals Django Deprecation Timeline

Calling QuerySet.aiterator() after prefetch_related() without providing a chunk_size will raise ValueError. The Extract and Trunc database functions will capture the current timezone in migrations when the tzinfo argument is omitted and USE_TZ is True.

Tutorial Writing your first Django app, part 3

It’s a very common idiom to use get() and raise Http404 if the object doesn’t exist. Django provides a shortcut.

Reference Generic display views

classdjango.views.generic.list.ListView : A page representing a list of objects. classdjango.views.generic.list.BaseListView : A base view for displaying a list of objects.

Reference Date-based mixins

classDateMixin[source] : A mixin class providing common behavior for all date-based views.

Reference Single object mixins

classdjango.views.generic.detail.SingleObjectMixin : Provides a mechanism for looking up an object associated with the current HTTP request.