django: db - many to one

models 模块中的对象有三种对应关系：多对一，多对多，一对一。本讲说明多对一关系。

blog/models.py:

from django.db import models

class Employee(models.Model):
    name = models.CharField(max_length=20)  # map 'name' field to db

    def __unicode__(self):
        return self.name

class Entry(models.Model):
    name = models.CharField(max_length=20)

    def __unicode__(self):
        return self.name

class Blog(models.Model):
    name = models.CharField(max_length=20)
    entry = models.ForeignKey(Entry)        # Many-To-One Map: Blogs - Entry

    def __unicode__(self):
        return self.name

Debug 查看使用方式：

[root@bogon csvt03]#  ipython manage.py shell
reload ipy_profile_none
reload ipy_user_conf
Python 2.7. (default, Oct   , ::)
Type "copyright", "credits" or "license" for more information.

IPython 0.8. -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object'. ?object also works, ?? prints more.

In []:

In []: from blog.models import  Entry , Blog

In []: Entry.objects.all()
Out[]: [<Entry: eli>, <Entry: wu>, <Entry: min>]

In []: Blog.objects.all()
Out[]: []

In []: blog=Blog(name='blog',entry=Entry.objects.all()[])

In []: blog
Out[]: <Blog: blog>

In []: blog.save()

In []: blog2=Blog(name='blog2',entry=Entry.objects.all()[])

In []: blog2.save()

In []: blog3=Blog(name='blog3',entry=Entry.objects.all()[])

In []: blog3.save()

MySQL 结果：

mysql> select * from blog_entry;
+----+------+
| id | name |
+----+------+
|   | eli  |
|   | wu   |
|   | min  |
+----+------+
 rows in set (0.00 sec)

mysql> select * from blog_blog;
+----+-------+----------+
| id | name  | entry_id |
+----+-------+----------+
|   | blog  |         |
|   | blog2 |         |
|   | blog3 |         |
+----+-------+----------+
 rows in set (0.00 sec)