Question

我有四个模型，每个模型都包含自己的数据。这些模型是：

类别（包含department_id外键）
部门（包含数据，没有外键）
ProductCategory（仅包含product_id和category_id的联接表）
产品（不包含外键的数据）

# models.py (excluded the rest for brevity)

from django.db import models

class Department(models.Model):
    department_id = models.AutoField(primary_key=True)
    name = models.CharField(max_length=100)
    description = models.CharField(max_length=1000, blank=True, null=True)

    class Meta:
        managed = False
        db_table = 'department'


class Category(models.Model):
    category_id = models.AutoField(primary_key=True)
    #department_id = models.IntegerField()
    department = models.ForeignKey(Department, on_delete=models.CASCADE)
    name = models.CharField(max_length=100)
    description = models.CharField(max_length=1000, blank=True, null=True)

    class Meta:
        managed = False
        db_table = 'category'

class Product(models.Model):
    product_id = models.AutoField(primary_key=True)
    name = models.CharField(max_length=100)
    description = models.CharField(max_length=1000)
    price = models.DecimalField(max_digits=10, decimal_places=2)
    discounted_price = models.DecimalField(max_digits=10, decimal_places=2)
    image = models.CharField(max_length=150, blank=True, null=True)
    image_2 = models.CharField(max_length=150, blank=True, null=True)
    thumbnail = models.CharField(max_length=150, blank=True, null=True)
    display = models.SmallIntegerField()

    class Meta:
        managed = False
        db_table = 'product'

class ProductCategory(models.Model):
    product = models.ForeignKey(Product, on_delete=models.CASCADE)
    category = models.ForeignKey(Category, on_delete=models.CASCADE)

    class Meta:
        managed = False
        db_table = 'product_category'
        unique_together = (('product', 'category'),)

从端点开始，我需要将所有产品归入部门，并以以下格式返回响应：

"rows": [
    {
      "product_id": integer,
      "name": string,
      "description": string,
      "price": string,
      "discounted_price": string,
      "thumbnail": string
    }
]

这是端点：

path('products/inDepartment/<int:department_id>/', ProductViewSet.as_view({"get": "get_products_by_department"}))

我该怎么做？我被下面的代码困住了：

# products.py

def get_products_by_department(self, request, department_id):
        """
        Get a list of Products of Departments
        """
        categories = Category.objects.filter(department_id=department_id).values('category_id')

        for item in categories:
          category_id = item['category_id']
          products = ProductCategory.objects.filter(category_id=category_id).values(
            'product_id', name=F('product__name'), description=F('product__description'),
          price=F('product__price'), discounted_price=F('product__discounted_price'), thumbnail=F('product__thumbnail'))

        # Return response
        if products.exists():
          return Response(products, 200)
        else:
          return Response(products, 204)

上面的代码可以正常工作，并且给我正确的响应，但是我不确定我是否正确地执行了查询？我应该使用循环还是没有循环的Django更好的方法？

Answer 1

Django的ORM允许反向关系查找。 https://docs.djangoproject.com/en/2.2/topics/db/queries/#lookups-that-span-relationships

categories = Category.objects.filter(department_id=department_id)    
products = Product.objects.filter(productcategory__category__in=categories)

Django加入非托管表

1 个答案: