How to get objects using a ForeignKey field through another ForeignKey in Django?

Question

My models.py is something like this:

class Department(models.Model):
    name = models.CharField(max_length=255)

class Category(models.Model):
    name = models.CharField(max_length=255)
    department = models.ForeignKey(Department, related_name="categories")

class Product(models.Model):
    name = models.CharField(max_length=255)
    category = models.ForeignKey(Category, related_name="products")

As you can see, the product model does not have a direct connection to the department, it only has one through the category model. However, in my department details for < Department X >, I want to get all the products that have a category that has the department < Department X >. Is there any way to do it with one query? I don't want to use a for loop for this. Thanks!

Alasdair · Accepted Answer · 2017-10-24 15:04:24Z

3

You can use the double underscore notation to look up fields in related models, for example:

department = Department.objects.get(name='X')
products = Product.objects.filter(category__department=department)

Or, if you don't already have the department instance, you can filter by department name:

products = Product.objects.filter(category__department__name='X')

answered Oct 24, 2017 at 15:04

Alasdair

310k59 gold badges605 silver badges534 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

rajkris · Accepted Answer · 2017-10-24 15:06:11Z

2

Maybe something like this:

Product.objects.filter(category__department=<DepartmentX>)

edited Oct 24, 2017 at 15:06

answered Oct 24, 2017 at 15:05

rajkris

1,7931 gold badge11 silver badges17 bronze badges

5 Comments

rajkris Over a year ago

@mohammedqudah i dont think we need to delete this, since they are not the same answer

mohammedgqudah Over a year ago

yeh but the <DepartmentX> require one more line of code ;0

rajkris Over a year ago

The question already mentions the <departmentx> thing, so I suppose we don't need to mention that in the answer, and in addition to the question is not about fetching the <DepartmentX>

Alasdair Over a year ago

@mohammedqudah it's ok to have more than one answer to a question, please don't ask users to delete their answers. In the view, there's a good chance that the department will have been fetched already, so querying category__department=<DepartmentX> is a good approach.

mohammedgqudah Over a year ago

i am sorry. : )

Collectives™ on Stack Overflow

How to get objects using a ForeignKey field through another ForeignKey in Django?

2 Answers 2

Comments

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related