Reference Query Expressions Built-in ExpressionsSubquery() expressions

Subquery() that returns a boolean value and Exists() may be used as a condition in When expressions, or to directly filter a queryset: This will ensure that the subquery will not be added to the SELECT columns, which may result …

Reference QuerySet API reference QuerySet APIMethods that return new QuerySets

exclude(*args,**kwargs) Returns a new QuerySet containing objects that do not match the given lookup parameters. The lookup parameters (**kwargs) should be in the format described in Field lookups below.

Reference QuerySet API reference QuerySet APIMethods that return new QuerySets

union(*other_qs,all=False) Uses SQL’s UNION operator to combine the results of two or more QuerySets. For example: The UNION operator selects only distinct values by default. To allow duplicate values, use the all=True argument.

Reference QuerySet API reference QuerySet APIMethods that do not return QuerySets

latest(*fields) alatest(*fields) Asynchronous version: alatest() Returns the latest object in the table based on the given field(s).

Reference QuerySet API reference QuerySet APIField lookups

In a given iterable; often a list, tuple, or queryset. It’s not a common use case, but strings (being iterables) are accepted.

Reference QuerySet API reference QuerySet APIField lookups

Range test (inclusive). Example: SQL equivalent: You can use range anywhere you can use BETWEEN in SQL — for dates, numbers and even characters.

Reference QuerySet API reference QuerySet APIField lookups

Case-sensitive regular expression match. The regular expression syntax is that of the database backend in use.

Reference The Django template language: for Python programmers

staticEngine.get_default()[source] : Returns the underlying Engine from the first configured DjangoTemplates engine. Raises ImproperlyConfigured if no engines are configured. Engine.from_string(template_code)[source] : Compiles the given template code and returns a Template object.

Reference Built-in template tags and filters Built-in tag reference

Loads a template and renders it with the current context. This is a way of “including” other templates within a template. The template name can either be a variable or a hardcoded (quoted) string, in either single or double quotes.

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 Retrieving objects

Use a subset of Python’s array-slicing syntax to limit your QuerySet to a certain number of results. This is the equivalent of SQL’s LIMIT and OFFSET clauses.

Topic guide Making queries Retrieving objects

Field lookups are how you specify the meat of an SQL WHERE clause. They’re specified as keyword arguments to the QuerySet methods filter(), exclude() and get(). Basic lookups keyword arguments take the form field__lookuptype=value. (That’s a double-underscore).

Topic guide Making queries Retrieving objects

The field lookups that equate to LIKE SQL statements (iexact, contains, icontains, startswith, istartswith, endswith and iendswith) will automatically escape the two special characters used in LIKE statements – the percent sign and the underscore.

Topic guide Performing raw SQL queries

The raw() manager method can be used to perform raw SQL queries that return model instances: Manager.raw(raw_query,params=(),translations=None) This method takes a raw SQL query, executes it, and returns a django.db.models.query.RawQuerySet instance.

Topic guide Performing raw SQL queries

Sometimes even Manager.raw() isn’t quite enough: you might need to perform queries that don’t map cleanly to models, or directly execute UPDATE, INSERT, or DELETE queries.

Topic guide Database transactions Database-specific notes

While SQLite supports savepoints, a flaw in the design of the sqlite3 module makes them hardly usable. When autocommit is enabled, savepoints don’t make sense. When it’s disabled, sqlite3 commits implicitly before savepoint statements.

Topic guide Managing files File storage

You can use a callable as the storage parameter for FileField or ImageField. This allows you to modify the used storage at runtime, selecting different storages for different environments, for example.

Topic guide Creating forms from models ModelForm

As you might expect, the ForeignKey and ManyToManyField model field types are special cases: ForeignKey is represented by django.forms.ModelChoiceField, which is a ChoiceField whose choices are a model QuerySet.

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Topic guide Creating forms from models ModelForm

Consider this set of models: With these models, the ModelForm subclasses above would be roughly equivalent to this (the only difference being the save() method, which we’ll discuss in a moment.):

Topic guide Testing tools Provided test case classes

classTransactionTestCase[source] TransactionTestCase inherits from SimpleTestCase to add some database-specific features: Resetting the database to a known state at the end of each test to ease testing and using the ORM. Database fixtures. Test skipping based on database backend features.