如何通过Django中的另一个ForeignKey使用ForeignKey字段获取对象？

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!

Answer 1

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')

Answer 2

也许是这样的：

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