获取存储在多对多字段中的所有唯一值 [英] Getting all unique values stored in a many-to-many field

问题描述

我有一个多对多的字段称为类别，我想得到存储在该字段中的不同值。

I have a many-to-many field called categories and I would like to get distinct values stored in that field.

以下是我的模型：

class Book (models.Model):
    categories=models.ManyToManyField(Category, related_name = 'categories', blank = True, null=True)

我的类别模型：

class Category (MPTTModel):
    category = models.CharField(max_length=250)
    parent = TreeForeignKey('self', blank=True, null=True, related_name='children')

我想获得与一本书相关的每一个类别。我如何做到这一点？

I'd like to get every single one of the categories related to a book. How would I do this?

推荐答案

如果你想获得与一个 ，do book_inst.category_set.all（）。不会有重复。

If you want to get categories related to one instance of book, do book_inst.category_set.all(). There will not be duplicates.

但我想，你想要得到所有与相关的类别 >任何 书，您可以：

But I think, you want to get all Categories which are related to any Book, you can do:

Category.objects.filter(categories__in=[Book.objects.all()]).distinct()

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