Using your suggestion returns no values:
In [9]: Subcategory.objects.values('name').exclude(business=None)
Out[9]: []
And there are subcategories:
In [10]: Subcategory.objects.values('name')
Out[10]: [{'name': u'Agricultural'}, {'name': u'Auctioneers & Estate
Agents'}, {'name': u'Construction & Maintenance'}, {'name': u'Dining &
Bars'}, {'name': u'Education & Childcare'}, {'name':
u'Entertainment'}, {'name': u'Financial & Business Services'},
{'name': u'Financial Banking '}, {'name': u'Health & Beauty'},
{'name': u'Home & Garden'}, {'name': u'Hospitality'}, {'name':
u'Legal'}, {'name': u'Leisure'}, {'name': u'Manufacturing'}, {'name':
u'Miscellaneous'}, {'name': u'Motoring & Repairs'}, {'name':
u'Services'}, {'name': u'Shopping/Retail '}, {'name': u'Transport &
Logistics'}, {'name': u'Education '}, {'name': u'Transport'}, {'name':
u'Horse Riding'}, {'name': u'Walking'}]
And there are business objects with subcategories (naming here is
confusing!)
Business.objects.values('cat__name')
Out[7]: [{'cat__name': u'Agricultural'}, {'cat__name':
u'Agricultural'}, {'cat__name': u'Agricultural'}, {'cat__name':
u'Agricultural'}, {'cat__name': u'Agricultural'}, {'cat__name':
u'Agricultural'}, {'cat__name': u'Legal'}, {'cat__name': u'Shopping/
Retail '}, {'cat__name': u'Financial Banking '}, {'cat__name':
u'Shopping/Retail '}, {'cat__name': u'Agricultural'}]
Also tried:
Subcategory.objects.values('name').exclude(directory=None)
FieldError: Cannot resolve keyword 'directory' into field. Choices
are: business, category, community, id, name, tourism
The problem could be that I have an additional level in that Business
is subcalssed to Directory like this:
class Category(models.Model):
name = models.CharField(max_length=12, unique=True)
description = models.TextField()
class Subcategory(models.Model):
category = models.ForeignKey(Category)
name = models.CharField(max_length=30, unique=True)
class Directory(models.Model):
name = models.CharField(max_length=60)
phone = models.CharField(max_length=15)
...
class Business(Directory):
cat = models.ForeignKey(Subcategory, limit_choices_to =
{'category__exact': 2})
Any help much appreciated. This is my second website in Django and
starting to become slightly competant, with much support from this
users group. Thanks.
Phoebe.
On Jan 30, 2:23 am, Malcolm Tredinnick <malc...@pointy-stick.com>
wrote:
> On Thu, 2009-01-29 at 06:44 -0800, phoebebright wrote:
> > I want a distinct list of all the 'cat__names' that exist in
> > Subcategory and have at least one entry in Business (Business is a
> > subclass of model Directory which might be the problem)
>
> > dir_query = Business.objects.all().select_related().distinct()
> > ...
> > subcats = dir_query.values('cat__name','cat').select_related().distinct
> > ()
>
> > But the SQL this generates has an additional field in theSELECT
> > statement which means the DISTINCT does not have the effect I want and
> > selects all entries.
>
> >SELECTDISTINCT `town_subcategory`.`name`, `town_business`.`cat_id`,
> > `town_directory`.`name`
> > FROM `town_business`
> > INNER JOIN `town_subcategory` ON (`town_business`.`cat_id` =
> > `town_subcategory`.`id`)
> > INNER JOIN `town_directory` ON (`town_business`.`directory_ptr_id` =
> > `town_directory`.`id`)
> > ORDER BY `town_directory`.`name` ASC
>
> > Is there some way of forcing the fields in theselectstatement
> > without having to write the whole SQL in raw format? Or another way
> > of writing the query?
>
> Even if you could do what you wanted here, it wouldn't solve your
> problem. You're implicitly using theselectfields and the inner join to
> enforce the "a name exists" constraint. Django won't just add an
> arbitrary table in via an extra inner join if it's not required.
>
> There's a better solution to your problem, though. It's a little hard to
> tell what the exact queryset will look like, since I don't understand
> your models entirely, but this should be close. Firstly, you want
> subcategory names, so that's the model to filter on. the constraint
> "must have at least one business" is a filter on the business related
> attribute being not-None:
>
> SubCategory.objects.values('name').exclude(business=None)
>
> Regards,
> Malcolm
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