Question

所以我想说我有三个模型：User，CarBrand，CarModel，CarCharacteristics。 CarCharacteristics模型描述了用户如何评价汽车的特征。因此，用户可以有许多CarCharacteristics个对象，而用户可以拥有多个CarCharacteristics。

这就是我的模型：

class User(models.Model):
    id = models.AutoField(primary_key=True)

class CarBrand(models.Model):
    idcar_brand = models.AutoField(primary_key=True)

class CarModel(models.Model):
    idcar_model = models.AutoField(primary_key=True)
    car_brand = models.ForeignKey(CarBrand, null=True, on_delete=models.SET_NULL)

class CarCharacteristics(models.Model):
    idcar_characteristics = models.AutoField(primary_key=True)
    user = models.ForeignKey(User, on_delete=models.PROTECT)
    car_model = models.ForeignKey(CarModel, on_delete=models.PROTECT)

我想要的是获取CarBrand有User的所有CarCharacteristics个对象。这就是我现在正在做的事情：

car_chars = CarCharacteristics.objects.filter(user=user_id)
car_brands_ids = []
for car_char in car_chars:
    brand_id = car_char.car_model.car_brand.idcar_brand
    if brand_id not in car_brands_ids:
        car_brands_ids.append(brand_id)
brands = CarBrand.objects.filter(idcar_brand__in=brand_ids)

有更简单的方法吗？如何获得存在CarModels的所有CarCharacteristics？

Answer 1

试试这个：

CarBrand.objects.exclude(carmodel__carcharacteristics__user=None).distinct()

Answer 2

我想我明白了。我认为这有效：

user_id = request.user.pk
brands = CarBrand.objects.exclude(~Q(carmodel__carcharacteristics__user=user_id))

修改

我上面的内容也与此相同：

user_id = request.user.pk car_models = CarModel.objects.filter(carcharacteristics__user=user_id) brands = CarBrand.objects.filter(carmodel__in=car_models).distinct()

Answer 3

CarBrand.objects.filter(carmodel__carcharacteristics__user=request.user).distinct()

我如何在Django中执行此查询？

3 个答案: