Thanks a lot!
On May 16, 10:28 pm, Rolando Espinoza La Fuente <dark...@gmail.com>
wrote:
> On Sun, May 16, 2010 at 6:41 PM, Odagi <fcmira...@gmail.com> wrote:
> > Hello users, I cannot realize the difference between the different
> > ways of extending a model. Suppose we have Place and Restaurant Models
> > (a Restaurant is an extension of a Place). I know 3 different ways of
> > define the data model:
>
> > 1. Multi-table inheritance:
>
> > class Place(models.Model): ...
> > class Restaurant(Place): ...
>
> restaurant table gets all fields from place,
> you can access all fields with single sql query
>
> > 2. OneToOne relationship:
>
> > class Place(models.Model): ...
> > class Restaurant(models.Model):
> > place = models.OneToOneField(Place, primary_key=True)
>
> You access "place" fields by using: restaurant.place
> with extra db call unless you use select_related('place')
>
>
>
> > 3. ForeignKey unique:
>
> > class Place(models.Model): ...
> > class Restaurant(models.Model):
> > place = models.ForeignKey(Place, unique=True)
>
> In the old days there wasn't OneToOneField and people
> used this method to have one-one relationship.
> If you need to use ForeignKey+unique, better use OneToOneField.
>
> One difference is the related name, with ForeignKey+unique
> you would need to use place.restaurant_set[0] to access related
> restaurant. Using OneToOneField just use place.restaurant.
>
> ~Rolando
>
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