Django通过不同于id生成分组 [英] Django generate group by different than id

问题描述

我要计算同一产品的用户数量

I want to count amount of Users for same Product

models.py

class Product(models.Model):
   pass
class User(models.Model):
   product = models.ForeignKey(Product)
   age = models.IntegerField(blank=True, null=True)

User.objects.filter(age__gt=18).annotate(product_count=Count('product_id'))

输出sql

SELECT
  "user"."product_id"
  COUNT("user"."product_id") AS "product_count"
FROM "user"
WHERE "user"."age" > 18
GROUP BY "user"."id";

所需的SQL ：

SELECT
  "user"."product_id"
  COUNT("user"."product_id") AS "product_count"
FROM "user"
WHERE "user"."age" > 18
GROUP BY "user"."product_id";

推荐答案

我认为这没有任何意义。您想要的可能是这样的：

I don't think that makes any sense. What you want is probably this:

Product.objects.annotate(user_count=Count('user'))

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