如何通过关系外键对Django模型中的查询集进行排序
我有以下型号 models.py如何通过关系外键对Django模型中的查询集进行排序,django,rest,model,foreign-keys,Django,Rest,Model,Foreign Keys,我有以下型号 models.py class Category(models.Model): label = models.CharField(max_length=100, unique=True) description = models.CharField(max_length=255, blank=True) class Expense(models.Model): description = models.CharField(max_length=25
class Category(models.Model):
label = models.CharField(max_length=100, unique=True)
description = models.CharField(max_length=255, blank=True)
class Expense(models.Model):
description = models.CharField(max_length=255, blank=True)
amount = models.DecimalField(max_digits=10, decimal_places=2, default=0.00)
category = models.ForeignKey(
Category,
on_delete=models.CASCADE,
null=True,
related_name='category'
)
我正在努力学习如何返回一个类别列表,该列表是按开支模型中挑选最多的类别排序的,如:
<Expense category=3>
<Expense category=3>
<Expense category=2>
<Expense category=3>
<Expense category=1>
<Expense category=1>
用Django的可爱的
我们可以利用以下方法实现这一目标:
from django.db.models import Count
...
queryset = Category.objects.annotate(expense_count=Count('expense')).order_by('-expense_count')
从django.db.models导入计数
Category.objects.annotation(expense\u count=count('Category')).order\u by('-expense\u count'))
这是基于您的模型定义,但我建议将相关的\u名称
修改为与费用
相关的术语,例如费用
。由于相关的\u名称
指示您用于反向查询的名称。只需在查询末尾添加.distinct('field-name')。像这样
queryset = Category.objects.order_by("-expense__expense").distinct('category')
queryset = Category.objects.annotate(
expense_count=Count('category')).order_by('-expense_count')
queryset = Category.objects.annotate(expense_count=Count('expense')).order_by('-expense_count')
from django.db.models import Count
...
queryset = Category.objects.annotate(expense_count=Count('expense')).order_by('-expense_count')
queryset = Category.objects.order_by("-expense__expense").distinct('category')