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[1.5.X] Fixed #19352 - Added an example in the QuerySet docs. 

Thanks colinkeenan for the suggestion.

Backport of ba2adc9c05 from master
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Tim Graham 2012-11-27 18:21:55 -05:00
parent 1c05619c1f
commit 931b0f8ccd
1 changed files with 11 additions and 6 deletions
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17
docs/topics/db/queries.txt
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@ -575,12 +575,17 @@ To select all blogs that contain an entry with *"Lennon"* in the headline
Blog.objects.filter(entry__headline__contains='Lennon').filter(
entry__pub_date__year=2008)
In this second example, the first filter restricted the queryset to all those
blogs linked to that particular type of entry. The second filter restricted
the set of blogs *further* to those that are also linked to the second type of
entry. The entries select by the second filter may or may not be the same as
the entries in the first filter. We are filtering the ``Blog`` items with each
filter statement, not the ``Entry`` items.
Suppose there is only one blog that had both entries containing *"Lennon"* and
entries from 2008, but that none of the entries from 2008 contained *"Lennon"*.
The first query would not return any blogs, but the second query would return
that one blog.
In the second example, the first filter restricts the queryset to all those
blogs linked to entries with *"Lennon"* in the headline. The second filter
restricts the set of blogs *further* to those that are also linked to entries
that were published in 2008. The entries selected by the second filter may or
may not be the same as the entries in the first filter. We are filtering the
``Blog`` items with each filter statement, not the ``Entry`` items.
All of this behavior also applies to
:meth:`~django.db.models.query.QuerySet.exclude`: all the conditions in a