Also, I think you need to add null=True to the ForeignKey, like this:
category = models.ForeignKey(Category,null=True, blank=True)
blank=True indicates the admin interface that a value can be omitted,
but null=True is necessary to indicate to the database that the column
can be NULL.
On 7/12/06, Phil Powell <[EMAIL PROTECTED]> wrote:
>
> Hi - I've got a bit of a conundrum.
>
> I have two models, Category and Photo which look something like this:
>
> class Category(models.Model):
> title = models.CharField(maxlength=80)
> slug = models.SlugField(prepopulate_from=("title",))
>
> class Photo(models.Model):
> catalogue_number = models.IntegerField(maxlength=80)
> slug = models.SlugField(prepopulate_from=("catalogue_number",))
> category = models.ForeignKey(Category,blank=True)
>
> There is a one-to-many relationship defined so that a Photo can be
> assigned a Category.
>
> Now, what I want to be able to do is get a list of Categories, but
> ONLY those Categories which have been assigned to one or more Photos.
>
> I can think of plenty of ugly ways to work around this, but wondered
> whether anyone had a graceful solution?
>
> -Phil
>
> >
>
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