Re: Filter by ForeignKey reference??

[Markus T.]

That's it - thanks a lot!!!
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Re: Filter by ForeignKey reference??

[Rajesh Dhawan]

> I have two simple models:
>
> class Country(models.Model):
>   name  = models.CharField(_("Name"), max_length=50,
> unique=True)
>
> class Profile(models.Model):
>   name  = models.CharField(_("Name"), max_length=50,
> unique=True)
>   country   = models.ForeignKey(Country)
>
>
> If I want to create a list of all countries that are actually
> referenced (i.e. used by at least one Profile entry), how would I code
> that in Django?
>
> Maybe something like (of course this is rubbush):
>
> referenced_countries = Country.objects.exclude
> (profile__country__isnull=True)

Try:
countries = Country.objects.filter(profile__pk__isnull=False).distinct
()

-RD

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Re: Filter by ForeignKey reference??

[Markus T.]

Thanks for your reply!

Your approach returns a list of dictionaries (or tuples if values_list
() is used).
Do you know of a straight forward way that returns a list of model
objects, like filter() or all()?
(I mean something smarter than looping the returned list of tuples and
creating a new list of model objects).

Thanks
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Re: Filter by ForeignKey reference??

[Martin Conte Mac Donell]

On Mon, Feb 2, 2009 at 11:59 PM, Martin Conte Mac Donell
 wrote:
> If you need country_id/country_name:
>
 Profile.objects.values('country__id', 
 'country__name').select_related('country').distinct()
> [{'country__name': u'Country1', 'country__id': 1}, {'country__name':
> u'Country3', 'country__id': 3}]
>
> Which run this query:
>
 Profile.objects.values('country__id', 
 'country__name').select_related('country').distinct().query.as_sql()
> ('SELECT DISTINCT "b_profile"."country_id", "b_country"."name" FROM
> "b_profile" INNER JOIN "b_country" ON ("b_profile"."country_id" =
> "b_country"."id")', ())

Also you can ommit select_related('country') which is implicit with
"country__name" and "country__id".

M.

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Re: Filter by ForeignKey reference??

[Martin Conte Mac Donell]

On Mon, Feb 2, 2009 at 10:11 PM, Markus T.  wrote:
>
> Hi,
>
> I have two simple models:
>
> class Country(models.Model):
>  name  = models.CharField(_("Name"), max_length=50,
> unique=True)
>
> class Profile(models.Model):
>  name  = models.CharField(_("Name"), max_length=50,
> unique=True)
>  country   = models.ForeignKey(Country)
>
>
> If I want to create a list of all countries that are actually
> referenced (i.e. used by at least one Profile entry), how would I code
> that in Django?

If you need country_id/country_name:

>>> Profile.objects.values('country__id', 
>>> 'country__name').select_related('country').distinct()
[{'country__name': u'Country1', 'country__id': 1}, {'country__name':
u'Country3', 'country__id': 3}]

Which run this query:

>>> Profile.objects.values('country__id', 
>>> 'country__name').select_related('country').distinct().query.as_sql()
('SELECT DISTINCT "b_profile"."country_id", "b_country"."name" FROM
"b_profile" INNER JOIN "b_country" ON ("b_profile"."country_id" =
"b_country"."id")', ())

M.

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Filter by ForeignKey reference??

[Markus T.]

Hi,

I have two simple models:

class Country(models.Model):
  name  = models.CharField(_("Name"), max_length=50,
unique=True)

class Profile(models.Model):
  name  = models.CharField(_("Name"), max_length=50,
unique=True)
  country   = models.ForeignKey(Country)


If I want to create a list of all countries that are actually
referenced (i.e. used by at least one Profile entry), how would I code
that in Django?

Maybe something like (of course this is rubbush):

referenced_countries = Country.objects.exclude
(profile__country__isnull=True)


Thanks for your help
Markus
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