data

sqlite> select * from author;

id      name    age

1       jim     12

2       tom     11

sqlite> select * from book;

id      name    author_id

1       learn java      1

2       learn python    1

3       learn c++       2

models.py

# -*- coding: UTF-8 -*-

from __future__ import unicode_literals

from django.db import models

# Create your models here.

class Author(models.Model):

    name = models.CharField(verbose_name='姓名', max_length=50)

    age = models.IntegerField(verbose_name='年龄')

class Book(models.Model):

    name = models.CharField(verbose_name='书名', max_length=100)

    author = models.ForeignKey(Author, verbose_name='作者')

执行语句

>>> Author.objects.filter(book__name='learn java')

[<Author: jim>]

>>> author = Author.objects.get(pk=1)

>>> author.book_set.all()

[<Book: learn java>, <Book: learn python>]

假如把类Book改成这样

class Book(models.Model):

    name = models.CharField(verbose_name='书名', max_length=100)

    author = models.ForeignKey(Author, verbose_name='作者', related_name='bs', related_query_name='b')

那么上面查询代码就应该写成这样

>>> Author.objects.filter(b__name='learn java')

[<Author: jim>]

>>> author = Author.objects.get(pk=1)

>>> author.bs.all()

[<Book: learn java>, <Book: learn python>]

如果book表里有两个字段都外键关联author表，这时related_name就非常有用了。