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[1.1.X] Fixed #12859 -- Clarified the documentation on using multiple tables with .update() calls. Thanks to dwillis for the report. 

Backport of r12515 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.1.X@12520 bcc190cf-cafb-0310-a4f2-bffc1f526a37
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Russell Keith-Magee 2010-02-23 13:29:52 +00:00
parent b9d1c5d9f6
commit 7c1671b480
1 changed files with 8 additions and 3 deletions
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11
docs/topics/db/queries.txt
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@ -778,7 +778,7 @@ a ``QuerySet``. You can do this with the ``update()`` method. For example::
You can only set non-relation fields and ``ForeignKey`` fields using this You can only set non-relation fields and ``ForeignKey`` fields using this
method. To update a non-relation field, provide the new value as a constant. method. To update a non-relation field, provide the new value as a constant.
To update ``ForeignKey`` fields, set the new value to be the new model To update ``ForeignKey`` fields, set the new value to be the new model
instance you want to point to. Example:: instance you want to point to. For example::
>>> b = Blog.objects.get(pk=1) >>> b = Blog.objects.get(pk=1)
@ -788,8 +788,13 @@ instance you want to point to. Example::
The ``update()`` method is applied instantly and doesn't return anything The ``update()`` method is applied instantly and doesn't return anything
(similar to ``delete()``). The only restriction on the ``QuerySet`` that is (similar to ``delete()``). The only restriction on the ``QuerySet`` that is
updated is that it can only access one database table, the model's main updated is that it can only access one database table, the model's main
table. So don't try to filter based on related fields or anything like that; table. You can filter based on related fields, but you can only update columns
it won't work. in the model's main table. Example::
>>> b = Blog.objects.get(pk=1)
# Update all the headlines belonging to this Blog.
>>> Entry.objects.select_related().filter(blog=b).update(headline='Everything is the same')
Be aware that the ``update()`` method is converted directly to an SQL Be aware that the ``update()`` method is converted directly to an SQL
statement. It is a bulk operation for direct updates. It doesn't run any statement. It is a bulk operation for direct updates. It doesn't run any