django foreignkey外键使用的例子 相当于left join

# 在models.py 中添加
# Person 模型有两个外键， School和Province
# 
class Province(models.Model):
  name = models.CharField('省份', max_length = 10)
  post = models.CharField('邮编', max_length = 10)
  def __str__ (self):#在Python2中用__unicode__替换__str__
    return self.name

# class School_Type(models.Model):
#   school_type = models.CharField('学校类别')

class School(models.Model):
  id = models.IntegerField('学校编号', primary_key=True)
  name = models.CharField('学校名称', max_length=200)
  address = models.CharField('学校地址', max_length=200)

  def __str__ (self):#在Python2中用__unicode__替换__str__
    return self.name




class Person(models.Model):
  name = models.CharField('姓名', max_length=50)
  age = models.IntegerField('年龄')
  address = models.CharField('地址', max_length=100)
  email = models.EmailField('电子邮件')
  school = models.ForeignKey(School, on_delete=models.CASCADE)
  province = models.ForeignKey(Province, on_delete = models.CASCADE)

# 因为Form的字段跟model的字段相同，所以我们直接使用 ModelForm

class PersonForm(ModelForm):
  class Meta:
    model = Person
    fields = '__all__'

views.py 中的view，可以直接使用 form.save() 来保存form

def person(request):
  if request.POST:
    form = PersonForm(request.POST)

    if form.is_valid():
      p = form.save()
      return HttpResponse(request, 'success')
    else:
      return HttpResponse(request, 'fail')
  else:
    form = PersonForm()
    person_list = Person.objects.all()
    # school_list = person_list.School_set.all()
    return render(request, 'person.html', locals())

{% extends 'base.html' %}

{% block content %}

  <form action="." method="POST">
  {% csrf_token %}
  {{ form }}
  <input type="submit" value='submit' />

  </form>

{#  #}
  {% for person in person_list %}

  <p>name:{{ person.name }}; age: {{ person.age }}; school:{{ person.school}}
     {{ person.province.post }}
  </p>
{% endfor %}
{#  {{ school_list }}#}

{% endblock %}