Re: 3 table many to many relationship

Merci beaucoup

On Wed, Apr 23, 2014 at 10:43 PM, Simon Charette <charette.s@gmail.com> wrote:

Django allows you to explicitly specify an intermediary model for many-to-many relationships with the `through` option.

class A(models.Model):
    b_set = models.ManyToMany('B', related_name='a_set', through='R')
    c_set = models.ManyToMany('C', related_name='a_set', through='R')

class B(models.Model):
    pass

class C(models.Model):
    pass

class R(models.Model):
    a = models.ForeignKey('A')
    b = models.ForeignKey('B')
    c = models.ForeignKey('C')

However you'll loose the ability of directly adding objects to relationships (A().b_set.create() won't work).
You'll need to explicitly create `R` instances instead: R.objects.create(a=a, b=b, c=c).

Simon

Le mercredi 23 avril 2014 23:24:04 UTC-4, Malik Rumi a écrit :

I was designing the models I will need for this project. I designed an intermediate table for two models, A and B, and then started to sketch out an intermediate table for two other models, A and C, when I realized that these two intermediate tables both use A, and further, the information in the second intermediate table will be a lot more valuable it if also shows the relationship C has to B.

I looked at the Many to Many documentation on the official Django site, but I don't see a discussion of this three table option. I have seen it elsewhere, so I assume it can be done. What I don't assume is the impact this has on performance and other issues I might not even anticipate. So, my questions:

   Can this three sided many to many intermediate table be created in Django?

    If it can, is it advisable, or are there better / more efficient ways of doing this, like with two intermediate tables as I was originally thinking?

thx.

--
You received this message because you are subscribed to a topic in the Google Groups "Django users" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/django-users/Z53HNI9t8Rw/unsubscribe.
To unsubscribe from this group and all its topics, send an email to django-users+unsubscribe@googlegroups.com.
To post to this group, send email to django-users@googlegroups.com.
Visit this group at http://groups.google.com/group/django-users.

To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/2e128d84-3e70-4bab-8b70-696eaaa369c1%40googlegroups.com.

For more options, visit https://groups.google.com/d/optout.

--
You received this message because you are subscribed to the Google Groups "Django users" group.
To unsubscribe from this group and stop receiving emails from it, send an email to django-users+unsubscribe@googlegroups.com.
To post to this group, send email to django-users@googlegroups.com.
Visit this group at http://groups.google.com/group/django-users.
To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/CAKd6oByv_%3Dif8JTtLi%3D5%2BtzUsS8K6MSuS_AG8ooYhUqX039Cng%40mail.gmail.com.
For more options, visit https://groups.google.com/d/optout.