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

git-svn-id: http://code.djangoproject.com/svn/django/trunk@12515 bcc190cf-cafb-0310-a4f2-bffc1f526a37
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Russell Keith-Magee 2010-02-23 13:20:27 +00:00
parent 745b89f6e1
commit c306b78150
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
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
instance you want to point to. Example::
instance you want to point to. For example::
>>> b = Blog.objects.get(pk=1)
@ -788,8 +788,13 @@ instance you want to point to. Example::
The ``update()`` method is applied instantly and returns the number of rows
affected by the query. The only restriction on the ``QuerySet`` that is
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;
it won't work.
table. You can filter based on related fields, but you can only update columns
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
statement. It is a bulk operation for direct updates. It doesn't run any