Re: .filter() and .exclude() don't add up

On Fri, Jul 26, 2013, Steve McConville <mcconville.steve@gmail.com> wrote:

>Firstly (and I don't think this is the cause of the problem) you're
>calling datetime.now() four times, which will give you four different
>datetimes (ie. the queries will not be completely identical).

Good point, I will address that.

> Secondly
>SQL uses a 3-valued logic (with null) so if any of the fields you're
>filtering on are nullable you may not be able to rely on the law of
>the excluded middle

So, if one of the fields can be Null, then *neither*:

queryset.filter(field=value)

queryset.exclude(field=value)

will match a record where it's Null?

In that case, is there a better - more reliable - way than using both .filter() and .exclude() with the same terms to split a queryset into all those items that match a filter, and all those that don't?

Thanks,

Daniele

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