Topic guide Performing raw SQL queries Performing raw queries

If you need to perform parameterized queries, you can use the params argument to raw(): params is a list or dictionary of parameters.

Topic guide Working with forms

In HTML, a form is a collection of elements inside <form>...</form> that allow a visitor to do things like enter text, select options, manipulate objects or controls, and so on, and then send that information back to the server.

Reference QuerySet API reference QuerySet APIField lookups

Exact match. If the value provided for comparison is None, it will be interpreted as an SQL NULL (see isnull for more details).

Reference Databases Oracle notes

The Oracle backend stores TextFields as NCLOB columns. Oracle imposes some limitations on the usage of such LOB columns in general: LOB columns may not be used as primary keys. LOB columns may not be used in indexes.

4.2 5.0 5.1

Reference Form fields Built-in Field classes

classNullBooleanField(**kwargs)[source] : - Default widget: NullBooleanSelect - Empty value: None - Normalizes to: A Python True, False or None value. - Validates nothing (i.e., it never raises a ValidationError).

Reference Query Expressions Built-in Expressions

classRawSQL(sql,params,output_field=None)[source] Sometimes database expressions can’t easily express a complex WHERE clause. In these edge cases, use the RawSQL expression.

Reference Model field reference Field options

Field.choices[source] A mapping or iterable in the format described below to use as choices for this field.

How-to How to write custom lookups

When using the above written abs lookup, the SQL produced will not use indexes efficiently in some cases. In particular, when we use change__abs__lt=27, this is equivalent to change__gt=-27 AND change__lt=27.

Internals Organization of the Django Project Steering council

The steering council selects Mergers as necessary to maintain their number at a minimum of three, in order to spread the workload and avoid over-burdening or burning out any individual Merger.

Reference GeoDjango Installation Platform-specific instructionsWindows

The OSGeo4W installer helps to install the PROJ, GDAL, and GEOS libraries required by GeoDjango. First, download the OSGeo4W installer, and run it. Select Express Web-GIS Install and click next. In the ‘Select Packages’ list, ensure that GDAL is selected.

Reference GeoDjango Tutorial Spatial Queries

When doing spatial queries, GeoDjango automatically transforms geometries if they’re in a different coordinate system.

Reference The messages framework Configuring the message engine

The messages framework can use different backends to store temporary messages. Django provides three built-in storage classes in django.contrib.messages: classstorage.session.SessionStorage : This class stores all messages inside of the request’s session. Therefore it requires Django’s contrib.sessions application.

Reference Databases Oracle notes

By default, the Oracle backend uses a RETURNING INTO clause to efficiently retrieve the value of an AutoField when inserting new rows.

Reference django-admin and manage.py Extra nicetiesSyntax coloring

The colors used for syntax highlighting can be customized. Django ships with three color palettes: dark, suited to terminals that show white text on a black background. This is the default palette.

Reference Form fields

Two fields are available for representing relationships between models: ModelChoiceField and ModelMultipleChoiceField. Both of these fields require a single queryset parameter that is used to create the choices for the field.

Reference Form fields Fields which handle relationships

By default, ModelChoiceField and ModelMultipleChoiceField use ModelChoiceIterator to generate their field choices. When iterated, ModelChoiceIterator yields 2-tuple choices containing ModelChoiceIteratorValue instances as the first value element in each choice.

Reference Widgets Built-in widgets

These widgets make use of the HTML elements <select>, <input type="checkbox">, and <input type="radio">. Widgets that render multiple choices have an option_template_name attribute that specifies the template used to render each choice.

Reference Query Expressions Built-in Expressions

Func() expressions are the base type of all expressions that involve database functions like COALESCE and LOWER, or aggregates like SUM.

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Reference Query Expressions Built-in Expressions

classSubquery(queryset,output_field=None)[source] You can add an explicit subquery to a QuerySet using the Subquery expression.

Reference Query Expressions Built-in ExpressionsSubquery() expressions

classExists(queryset)[source] Exists is a Subquery subclass that uses an SQL EXISTS statement. In many cases it will perform better than a subquery since the database is able to stop evaluation of the subquery when a first matching row is found.