先設(shè)置一個(gè)關(guān)于書本(book)的數(shù)據(jù)模型：
from django.db import modelsclass 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.nameclass 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
訪問外鍵(Foreign Key)值
當(dāng)你獲取一個(gè)ForeignKey 字段時(shí),你會(huì)得到相關(guān)的數(shù)據(jù)模型對(duì)象。 例如:
>>> b = Book.objects.get(id=50)>>> b.publisher<Publisher: Apress Publishing>>>> b.publisher.websiteu'http://www.apress.com/'
對(duì)于用`` ForeignKey`` 來定義的關(guān)系來說，在關(guān)系的另一端也能反向的追溯回來，只不過由于不對(duì)稱性的關(guān)系而稍有不同。 通過一個(gè)`` publisher`` 對(duì)象，直接獲取 books ，用 publisher.book_set.all() ，如下：
>>> p = Publisher.objects.get(name='Apress Publishing')>>> p.book_set.all()[<Book: The Django Book>, <Book: Dive Into Python>, ...]
實(shí)際上，book_set 只是一個(gè) QuerySet，所以它可以像QuerySet一樣,能實(shí)現(xiàn)數(shù)據(jù)過濾和分切，例如：
>>> p = Publisher.objects.get(name='Apress Publishing')>>> p.book_set.filter(name__icontains='django')[<Book: The Django Book>, <Book: Pro Django>]
屬性名稱book_set是由模型名稱的小寫(如book)加_set組成的。
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