我在Djangio乞讨，如果这是一个愚蠢的问题，请原谅。order_by()在Django中到底做了什么？

from django.db import models

class Book(models.Model):
    title = models.CharField(max_length=200)
    author = models.CharField(max_length=100)
    published_date = models.DateField()
    price = models.DecimalField(max_digits=10, decimal_places=2)

# 按照标题升序排序
books = Book.objects.all().order_by('title')

# 先按作者升序排序，如果作者相同，则按出版日期降序排序
books = Book.objects.all().order_by('author', '-published_date')

# 按照价格降序排序
books = Book.objects.all().order_by('-price')

# 过滤出价格大于20的书籍，并按出版日期升序排序
books = Book.objects.filter(price__gt=20).order_by('published_date')

from django.db.models import F, ExpressionWrapper, DecimalField

# 计算折后价格并按其排序
books = Book.objects.annotate(
    discounted_price=ExpressionWrapper(F('price') * (1 - F('discount')), output_field=DecimalField())
).order_by('discounted_price')