Topic guide Models Model methods

NOTE: Note that the delete() method for an object is not > necessarily called when deleting objects in bulk using a > QuerySet or as a result of a cascading > delete.

Topic guide Making queries

To represent database-table data in Python objects, Django uses an intuitive system: A model class represents a database table, and an instance of that class represents a particular record in the database table.

Topic guide Making queries Related objectsOne-to-many relationships

Subsequent accesses to the foreign key on the same object instance are cached. Example: Note that the select_related() QuerySet method recursively prepopulates the cache of all one-to-many relationships ahead of time. Example:

Topic guide Making queries Related objectsMany-to-many relationships

You would expect it to return the entry e. However, the filter condition, which traverses the many-to-many relationship between Entry and Author, yields an empty QuerySet.

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Topic guide Pagination

… you methods for accessing the items for each page: NOTE: Note that you can give Paginator a list/tuple, a Django QuerySet, > or any other object with a count() or __len__() method. When > determining the number of objects contained …

Reference Query Expressions Built-in Expressions

As well as being used in operations on single instances as above, F() can be used with update() to perform bulk updates on a QuerySet.

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Index

| | | | --- | --- | | - handle() (BaseCommand method) - handle_app_config() (AppCommand method) - handle_label() (LabelCommand method) - handle_no_permission() (AccessMixin method) - handle_raw_input() (FileUploadHandler method) - handler400 (in module django.conf.urls) - handler403 (in module django.conf.urls) - …

Index

| | | | --- | --- | | - m (LineString attribute) - (Point attribute) - mail_admins() (in module django.core.mail) - mail_managers() (in module django.core.mail) - make_aware() (in module django.utils.timezone) - make_list - template filter - make_naive() (in module …

How-to How to write custom lookups

You will need to ensure that this registration happens before you try to create any querysets using it. You could place the implementation in a models.py file, or register the lookup in the ready() method of an AppConfig.

Reference The syndication feed framework The high-level framework

This simple example, taken from a hypothetical police beat news site describes a feed of the latest five news items: To connect a URL to this feed, put an instance of the Feed object in your URLconf.

Reference Model instance reference

In addition to save(), delete(), a model object might have some of the following methods: Model.get_FOO_display() For every field that has choices set, the object will have a get_FOO_display() method, where FOO is the name of the field.

Topic guide Making queries Retrieving objects

Django offers a powerful and intuitive way to “follow” relationships in lookups, taking care of the SQL JOINs for you automatically, behind the scenes.

Topic guide Making queries Querying JSONField

To query based on a given dictionary key, use that key as the lookup name: To query a key for JSON null, None or JSONNull() can be used.

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Topic guide Making queries Querying JSONField

As with other fields, storing None as the field’s value will store it as SQL NULL. While not recommended, it is possible to store JSON scalar null instead of SQL NULL by using Value(None, JSONField()).

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Topic guide Making queries Querying JSONField

To query based on a given dictionary key, use that key as the lookup name: Multiple keys can be chained together to form a path lookup: If the key is an integer, it will be interpreted as an index transform …

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… Model index reference Constraints reference Model _meta API Related objects reference Model class reference Model Meta options Model instance reference QuerySet API reference Lookup API reference Query Expressions Conditional Expressions Database Functions Paginator Paginator class AsyncPaginator class Page class AsyncPage …

Index

… attribute) - contained - field lookup type - contains - field lookup type - contains() (GEOSGeometry method) - (in module django.db.models.query.QuerySet) - (OGRGeometry method) - (PreparedGeometry method) - contains_aggregate (Expression attribute) - contains_over_clause (Expression attribute) - contains_properly - field lookup …

Index

| | | | --- | --- | | - TabularInline (class in django.contrib.admin) - Tan (class in django.db.models.functions) - Task (class in django.tasks) - task (TaskResult attribute) - task() (in module django.tasks) - task_result (TaskContext attribute) - TaskContext (class …

Reference QuerySet API reference QuerySet APIMethods that return new QuerySets

values_list(*fields,flat=False,named=False) This is similar to values() except that instead of returning dictionaries, it returns tuples when iterated over.

Reference QuerySet API reference QuerySet APIMethods that do not return QuerySets

create(**kwargs) acreate(**kwargs) Asynchronous version: acreate() A convenience method for creating an object and saving it all in one step. Thus: and: are equivalent.