Ah, most enlightening and makes perfect sense, thanks Tom!
? 11 ?.?. 2553 ???? 21:45 Tom Evans <tevans...@googlemail.com> ?????:
> 2010/10/11 Jonathan Barratt <jonathan.barr...@knifeict.com>:
>> On 11 ?.?. 2010, at 21:05, Sithembewena Lloyd Dube wrote:
>> Note also that, AFAIK, multiple where criteria are accomplished by chaining
>> filters rather than providing them as a list to one filter call.
>> But I am new to Django myself, so if anyone corrects this advice - follow
>> their directions not mine! :)
>
> That's not quite right, both are suitable (and _can_ have different
> meanings, although not in this case).
>
> If you assume models like so:
>
> class Item:
> name = CharField
> type = ManyToManyField('Type')
>
> class Type:
> name = CharField
> enabled = BooleanField
> displayable = BooleanField
>
> then these two lines are different query sets:
>
> Item.objects.filter(type__enabled=True, type__displayable=True)
>
> Item.objects.filter(type__enabled=True).filter(type__displayable=True)
>
>
> The former selects Items with one or more associated Type instances
> that are both enabled and displayable. The latter selects Items that
> have one or more associated Type instances that are enabled and
> displayable, but not necessarily the on the same Type object.
>
> When the filter is not over a m2m field though, the two forms are
> largely equivalent.
>
> For more info see the manual:
>
> http://docs.djangoproject.com/en/1.2/topics/db/queries/#spanning-multi-valued-relationships
>
> Cheers
>
> Tom
>
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