On Tue, Mar 24, 2009 at 4:15 PM, Paulo Köch <paulo.k...@gmail.com> wrote:
>
> Does that generate a join or a not in? This is very relevant for
> performance.
>
> Cheers,
> Paulo Köch
>
>
>
> On Tue, Mar 24, 2009 at 20:13, Alex Gaynor <alex.gay...@gmail.com> wrote:
> >
> >
> > On Tue, Mar 24, 2009 at 4:05 PM, Konstantin S <ktechli...@gmail.com>
> wrote:
> >>
> >> Hello!
> >>
> >> I have two unrelated models that have one common field.
> >>
> >> class Media(models.Model):
> >> title = models.CharField(max_length=500)
> >> ...
> >>
> >> class Link(models.Model):
> >> title = models.CharField(max_length=500)
> >> ...
> >>
> >> Now I want to select those objects from the Media model that do not
> >> exist in the Link model if we compare them only by 'title' field. In
> >> raw SQL it looks like this:
> >>
> >> select * from Media left join Link on Media.title=Link.title where
> >> Link.title is null;
> >>
> >> Is it possible to make the same thing by Django ORM only ?
> >>
> >>
> >
> > So to be clear you want all items from Media for which there isn't a link
> > with that title, in the ORM that would look like:
> >
> > Media.objects.exclude(title__in=Link.objects.values('title'))
> >
> > Alex
> >
> > --
> > "I disapprove of what you say, but I will defend to the death your right
> to
> > say it." --Voltaire
> > "The people's good is the highest law."--Cicero
> >
> > >
> >
>
> >
>
No, it's done using a subquery.
Alex
--
"I disapprove of what you say, but I will defend to the death your right to
say it." --Voltaire
"The people's good is the highest law."--Cicero
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