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Fixed #14120 - Document get() in Making Queries - thanks danielr and adamv for work on the patch.
git-svn-id: http://code.djangoproject.com/svn/django/trunk@14820 bcc190cf-cafb-0310-a4f2-bffc1f526a37
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@ -163,6 +163,7 @@ That's because ``Entry.objects``, the root ``QuerySet``, is a special case
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that cannot be evaluated. The ``all()`` method returns a ``QuerySet`` that
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*can* be evaluated.)
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Retrieving specific objects with filters
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----------------------------------------
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@ -258,12 +259,43 @@ aren't fetched from the database until you "ask" for them. When you do, the
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``QuerySet`` is *evaluated* by accessing the database. For more details on
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exactly when evaluation takes place, see :ref:`when-querysets-are-evaluated`.
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Other QuerySet methods
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~~~~~~~~~~~~~~~~~~~~~~
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Most of the time you'll use ``all()``, ``filter()`` and ``exclude()`` when you
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need to look up objects from the database. However, that's far from all there is; see the :ref:`QuerySet API Reference <queryset-api>` for a complete list
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of all the various ``QuerySet`` methods.
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.. _retrieving-single-object-with-get:
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Retrieving a single object with get
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-----------------------------------
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``.filter()`` will always give you a ``QuerySet``, even if only a single
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object matches the query - in this case, it will be a ``QuerySet`` containing
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a single element.
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If you know there is only one object that matches your query, you can use
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the ``get()`` method on a `Manager` which returns the object directly::
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>>> one_entry = Entry.objects.get(pk=1)
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You can use any query expression with ``get()``, just like with ``filter()`` -
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again, see `Field lookups`_ below.
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Note that there is a difference between using ``.get()``, and using
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``.filter()`` with a slice of ``[0]``. If there are no results that match the
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query, ``.get()`` will raise a ``DoesNotExist`` exception. This exception is an
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attribute of the model class that the query is being performed on - so in the
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code above, if there is no ``Entry`` object with a primary key of 1, Django will
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raise ``Entry.DoesNotExist``.
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Similarly, Django will complain if more than one item matches the ``get()``
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query. In this case, it will raise ``MultipleObjectsReturned``, which again is
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an attribute of the model class itself.
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Other QuerySet methods
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----------------------
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Most of the time you'll use ``all()``, ``get()``, ``filter()`` and ``exclude()``
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when you need to look up objects from the database. However, that's far from all
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there is; see the :ref:`QuerySet API Reference <queryset-api>` for a complete
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list of all the various ``QuerySet`` methods.
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.. _limiting-querysets:
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@ -304,7 +336,7 @@ This is roughly equivalent to::
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Note, however, that the first of these will raise ``IndexError`` while the
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second will raise ``DoesNotExist`` if no objects match the given criteria. See
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``get()`` for more details.
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:meth:`~django.db.models.QuerySet.get` for more details.
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.. _field-lookups-intro:
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