Django查询来自子节点的父节点

from django.db import models

class Category(models.Model):
    name = models.CharField(max_length=100)
    parent = models.ForeignKey('self', null=True, blank=True, related_name='children', on_delete=models.CASCADE)

class Product(models.Model):
    name = models.CharField(max_length=100)
    category = models.ForeignKey(Category, on_delete=models.CASCADE)

# 获取特定子类别的父类别
child_category = Category.objects.get(id=child_id)
parent_category = child_category.parent

# 或者使用related_name查询所有子类别的父类别
parent_category = Category.objects.get(id=parent_id)
all_children = parent_category.children.all()

from django.shortcuts import get_object_or_404

try:
    child_category = Category.objects.get(id=child_id)
    parent_category = child_category.parent
except Category.DoesNotExist:
    # 处理不存在的情况
    parent_category = None

# 使用select_related优化一对一或外键关系查询
categories = Category.objects.select_related('parent').all()

# 使用prefetch_related优化多对多或反向一对一关系查询
categories = Category.objects.prefetch_related('children').all()