基于另一个模型查询集长度的Django模型order_by

from django.db import models

class Post(models.Model):
    title = models.CharField(max_length=200)
    content = models.TextField()
    pub_date = models.DateTimeField('date published')

# 按发布日期升序排序
posts = Post.objects.order_by('pub_date')

# 按发布日期降序排序
posts = Post.objects.order_by('-pub_date')

from django.db import models

class Author(models.Model):
    name = models.CharField(max_length=100)

class Book(models.Model):
    title = models.CharField(max_length=200)
    author = models.ForeignKey(Author, on_delete=models.CASCADE)

from django.db.models import Count

# 按作者写的书的数量降序排序
authors = Author.objects.annotate(num_books=Count('book')).order_by('-num_books')