Django 选择一个计数

Question

我是 Django 的新手，我想获得用户拥有的客户总数（我的用户将通过我的网站销售东西）所以我有一个 table 称为订单，我将 user_id 购买的用户和 product_id 正在购买的用户。每个产品 ID 都与具有用户（我正在查询的用户）的产品相关：

select COUNT(distinct(o.user_id)) as total_clients from `order` o 
    inner join product p on p.id=o.product_id where p.user_id=32;

用户 ID 32 已登录，我想告诉他有多少客户购买了他的产品。

我想在 get 而不是 filter 中执行此操作，因为它更有意义。

这是我的逻辑告诉我要写的内容：

clients = Order.objects.get(
    status = Order.COMPLETED,
    product__user = self.user
).annotate(
    total_clients = Count( 'user', distinct = True )
)

return clients.total_clients

.这就是它 returns:

Exception Type: MultipleObjectsReturned
Exception Value:  get() returned more than one Order -- it returned 2!

我可能会运行查询而不是使用 orm，但我不想那样。这是一个相当简单的查询，我确信 Django 处理起来非常容易，我想避免在我的代码中写入字符串。

这是我的模型设置：

class UserProfile( models.Model ):
    user = models.OneToOneField( User, related_name = 'profile' )
    ....


    def get_total_clients( self ):
        clients = Order.objects.get(
            status = Order.COMPLETED,
            product__user = self.user
        ).annotate(
            total_clients = Count( 'user', distinct = True )
        )

        return clients.total_clients


class Order( models.Model ):
    PENDING = 0
    COMPLETED = 1
    REFUNDED = 2

    STATUS_CHOICES = (
        (PENDING, "Pending"),
        (COMPLETED, "Completed"),
        (REFUNDED, "Refunded"),
    )

    user = models.ForeignKey( User, related_name = "orders" )
    product = models.ForeignKey( Product, related_name = "orders" )
    amount = models.DecimalField( max_digits = 6, decimal_places = 2, default = 0.00 )
    status = models.SmallIntegerField(
        choices = STATUS_CHOICES, default = PENDING, db_index = True
    )


class Product( models.Model ):
    user = models.ForeignKey( User, related_name = "unlocks" )
    name = models.CharField( max_length = 255 )

Answer 1

Django 查询集有一个 count 方法：

clients = Order.objects.filter(
                            status = Order.COMPLETED,
                            product__user = self.user
             )
return clients.count()

Answer 2

如果我没听错，您感兴趣的是从用户那里订购产品的消费者数量。一些 docs，可能会有帮助。

我的建议是：

result = Product.objects.distinct().filter(
    # or any query:
    orders__status=Order.COMPLETED,
    user=default_user

).aggregate( # see the difference between aggregate() and annotate()
    total_users=Count('orders__user', distinct=True)
)

我希望结果是：{'total_users': NUM_OF_USERS}

在原始 SQL 中，它将类似于：

SELECT DISTINCT COUNT(DISTINCT "main_order"."user_id") AS 
"total_users" FROM "main_product" INNER JOIN "main_order" ON (     
"main_product"."id" = "main_order"."product_id" ) WHERE 
("main_order"."status" = STATUS AND "main_product"."user_id" = USER_ID)

这是你想要的吗？

Django 选择一个计数

Django selecting a count

django

django-models

django-orm