多对多以及如何从queryset获取查询集

I have following models:

我有以下型号：

class Product(models.Model):
    name = CharField(max_length=30)

class Store(models.Model):
    name = CharField(max_length=30)
    product = models.ManyToManyField(Product)

How to get Stores with product named product_name and also, get all the products (except the product with name product_name) ? Is it possible to make it in one query? In raw SQL it would be simple JOINs. Not sure how to implement it via Django.

如何使用名为product_name的产品获取商店，并获取所有产品（名称为product_name的产品除外）？是否可以在一个查询中进行？在原始SQL中，它将是简单的JOIN。不知道如何通过Django实现它。

3 个解决方案

#1

You can actually do these things with Django due to it's lazy queryset evaluation. Django's in field lookup accepts both lists and querysets. The following will create a nested SQL code:

你可以用Django实际做这些事情，因为它是懒惰的查询集评估。 Django的字段查找接受列表和查询集。以下将创建嵌套的SQL代码：

products = Product.objects.filter(store_set__in=stores_qs)
stores_qs = Store.objects.filter(product__name='product_name')

Here are the Django in docs.

这是文档中的Django。

#2

You should be able to filter the stores based on an attribute of Product, and then prefetch_related of the retrieved objects.

您应该能够根据Product的属性过滤存储，然后prefetch_related检索到的对象。

Store.objects.filter(product__name="product_name").prefetch_related('product')

This should hit the database the fewest times to achieve what you are looking for - twice.

这应该以最少的时间到达数据库以实现您正在寻找的 - 两次。

Further documentation can be found here.

可在此处找到更多文档。

#3

Get Stores with product named "product_name" :

使用名为“product_name”的产品获取商店：

Store.objects.filter(product__name='product_name')

Get all the products except the product with name "product_name":

获取名称为“product_name”的产品以外的所有产品：

Product.objects.exclude(name='product_name')

#1