booktest-7查询-自关联

1.从一到多和从多到一的关联查询

2.通过模型类实现关联查询

3.自关联-一种特殊的一对多

class AreaInfo(models.Model):
    atitle=models.CharField(max_length=20)
    #关系属性
    aparent=models.ForeignKey('self',on_delete=models.CASCADE,null=True,blank=True)

4.执行迁移

5.增加视图函数

def areas(request):
    #获取广州市的信息
    area = AreaInfo.objects.get(atitle='广州市')
    #获取广州市的上级地区
    parent = area.aparent
    #获取广州市的下级地区
    children = area.areainfo_set.all()
    return  render(request,'booktest/areas.html',{'area':area,'parent':parent,'children':children})

6.增加视图模板

    
    


当前地区
{{area.atitle}}

父级地区
{{parent.atitle}}

下级地区

    {% for child in children%}
        
{{child.atitle}}
    {% endfor %}

7.增加路由

from django.conf.urls import url
from . import views

urlpatterns = [
    url(r'^index$', views.index),
    url(r'^create$', views.create),
    url(r'^delete(\d+)$', views.delete),
    url(r'^areas$', views.areas),
]

8.访问http://127.0.0.1:8000/areas