Reference PostgreSQL specific model fields Range FieldsQuerying Range Fields

Range fields support the standard lookups: lt, gt, lte and gte. These are not particularly helpful - they compare the lower bounds first and then the upper bounds only if necessary.

Reference Form fields Fields which handle relationships

classModelMultipleChoiceField(**kwargs) : - Default widget: SelectMultiple - Empty value: An empty QuerySet (self.queryset.none()) - Normalizes to: A QuerySet of model instances. - Validates that every id in the given list of values exists in the queryset.

Topic guide Aggregation Generating aggregates for each item in a QuerySet

… most aggregates, there is no way to avoid this problem, however, the Count aggregate has a distinct parameter that may help: NOTE: In order to understand what happens in your query, consider inspecting the > query property of your QuerySet.

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.

Topic guide Django shortcut functions

get_object_or_404(klass,*args,**kwargs) : Calls get() on a given model manager, but it raises Http404 instead of the model’s DoesNotExist exception.

Index

… quarter - field lookup type - 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) |

Reference Settings Core SettingsDATABASES

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

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 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.

Topic guide Django shortcut functions

get_list_or_404(klass,*args,**kwargs) : Returns the result of filter() on a given model manager cast to a list, raising Http404 if the resulting list is empty.

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) - Abs (class in django.db.models.functions) - ABSOLUTE_URL_OVERRIDES - setting - abstract (Options attribute) - abulk_create() (in module django.db.models.query.QuerySet) - …

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 …

Tutorial Writing your first Django app, part 3 Raising a 404 error

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

Design philosophies Database API

This is also why the select_related() QuerySet method exists. It’s an optional performance booster for the common case of selecting “every related object.”

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 : 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.