django - Django过滤查询外键

Question

我正在努力为我的项目获取正确的查询。
这是一个例子或我的模型:

from django.db import models

class Publisher(models.Model):
    name = models.CharField(max_length=30)
    address = models.CharField(max_length=50)
    city = models.CharField(max_length=60)
    state_province = models.CharField(max_length=30)
    country = models.CharField(max_length=50)
    website = models.URLField()

    def __unicode__(self):
        return self.name

class Author(models.Model):
    first_name = models.CharField(max_length=30)
    last_name = models.CharField(max_length=40)
    email = models.EmailField()

    def __unicode__(self):
        return u'%s %s' % (self.first_name, self.last_name)

class Book(models.Model):
    title = models.CharField(max_length=100)
    authors = models.ManyToManyField(Author)
    publisher = models.ForeignKey(Publisher)
    publication_date = models.DateField()

    def __unicode__(self):
        return self.title

例如，我如何从书类中获取出版商？我想让所有以“hello”开头的书的出版商都为？
谢谢

Answer 1

如果要获取发布者，则必须从Publisher开始。这意味着您必须向后查询Book→Publisher关系。这是文档对此的评价:
Lookups that span relationships

To span a relationship, just use the field name of related fields across models, separated by double underscores, until you get to the field you want

...

To refer to a “reverse” relationship, just use the lowercase name of the model.

查询:

Publisher.objects.filter(book__title__startswith='hello')