ManyToMany模型关系Django

Question

I have two models:

class University(models.Model):
    name = models.CharField(max_length=50)
    address = models.CharField(max_length=50, null=True, blank=True)
    city = models.CharField(max_length=30, null=True, blank=True)
    country = CountryField(null=True, blank=True)
    created_at = models.DateTimeField(auto_now_add=True)
    modified_at = models.DateTimeField(auto_now=True)
    departments = models.ManyToManyField(Department)


class Department(models.Model):
    name = models.CharField(max_length=50)
    address = models.CharField(max_length=50, null=True, blank=True)
    created_at = models.DateTimeField(auto_now_add=True)
    modified_at = models.DateTimeField(auto_now=True)

I want to University have many Departments and vice versa which works fine. But I also want to store more departments individually for one university.

For instance:

University1 has Department1 and Department2.

University2 has Department1.

I want those departments store individually for each university. Now when I update Department1, ofcourse every University which has that school will see changes. I don't want that. I want to update Department1 but only for the University1 record. Department1 in University2 shouldn't be updated.

I assume that adding through option with intermediate model wouldn't help. What's the best solution?

Answer 1

For the first part of your question

But I also want to store more departments individually for one university.

• You can crate the departments and only add them to the university you want them to have a relationship with.

For the second part of your question

I want to update Department1 but only for the University1 record. Department1 in University2 shouldn't be updated

• You should add through tables. A through table defines the relationship between two models and it's purpose is to store what is unique to each specific relationship.

So if you want to update Department 1 for all universities you update Department 1's instance.

If you want to only update Department 1 with something unique between Department 1 and University 1, that goes in the through table between the two models.