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Diffstat (limited to 'docs')
| -rw-r--r-- | docs/db-api.txt | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/docs/db-api.txt b/docs/db-api.txt index 342f635219..c37ebd083a 100644 --- a/docs/db-api.txt +++ b/docs/db-api.txt @@ -1972,6 +1972,34 @@ complete query set:: Entry.objects.all().delete() +Updating multiple objects at once +================================= + +**New in Django development version** + +Sometimes you want to set a field to a particular value for all the objects in +a queryset. You can do this with the ``update()`` method. For example:: + + # Update all the headlings to the same value. + Entry.objects.all().update(headline='Everything is the same') + +You can only set non-relation fields and ``ForeignKey`` fields using this +method and the value you set the field to must be a normal Python value (you +can't set a field to be equal to some other field at the moment). + +To update ``ForeignKey`` fields, set the new value to be the new model +instance you want to point to. Example:: + + b = Blog.objects.get(pk=1) + # Make all entries belong to this blog. + Entry.objects.all().update(blog=b) + +The ``update()`` method is applied instantly and doesn't return anything +(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 +table. So don't try to filter based on related fields or anything like that; +it won't work. + Extra instance methods ====================== |