I want to store some additional information in that, automatically created, ManyToMany join-table. How would I do that in Django?
In my case I have two tables: "Employees" and "Projects". What I want to store is how much each of the employees receives per hour of work in each of the projects, since those values are not the same. So, how would I do that?
What occurred to me was to, instead of the method "ManyToManyField", create explicitly a third class/table to store those new informations and to set its relationship with "Employees" and "Projects" using the "ForeignKey" method. I'm pretty sure it will work, but is this the best approach?
To add data into ManyToMany field with Python Django, we can use the add method. This will add the entry for the association table between my_obj and categories .
Behind the scenes, Django creates an intermediary join table to represent the many-to-many relationship. By default, this table name is generated using the name of the many-to-many field and the name of the table for the model that contains it.
One to many relationships in Django models. To define a one to many relationship in Django models you use the ForeignKey data type on the model that has the many records (e.g. on the Item model). Listing 7-22 illustrates a sample of a one to many Django relationship.
A ManyToMany field is used when a model needs to reference multiple instances of another model. Use cases include: A user needs to assign multiple categories to a blog post. A user wants to add multiple blog posts to a publication.
Here is example of what you want to achieve:
http://docs.djangoproject.com/en/dev/topics/db/models/#extra-fields-on-many-to-many-relationships
In case link ever breaks:
from django.db import models class Person(models.Model): name = models.CharField(max_length=128) def __str__(self): # __unicode__ on Python 2 return self.name class Group(models.Model): name = models.CharField(max_length=128) members = models.ManyToManyField(Person, through='Membership') def __str__(self): # __unicode__ on Python 2 return self.name class Membership(models.Model): person = models.ForeignKey(Person) group = models.ForeignKey(Group) date_joined = models.DateField() invite_reason = models.CharField(max_length=64)
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