关于python+django操作数据库中的表

class C(models.Model):
   name = models.CharField(max_length=32) 

class B(models.Model):
   name = models.CharField(max_length=32) 
   b = models.ForeignKey(C) 

class A(models.Model):
    name = models.CharField(max_length=32) 

    a = models.ForeignKey(B) 
    def __unicode__(self):
        return self.name

def add(request):
    tmpc = C.objects.create(name=‘zs‘)
    tmpb = B.objects.create(name = ‘ls‘, b = tmpc)
    A.objects.create(name = ‘ww‘, a = tmpb)
    return HttpResponse("OK")

def test(request):
    a = A.objects.get(name = ‘ww‘)
    str1 = a.name
    str2 = a.a.name
    str3 = a.a.b.name
    print "str1=%s,str2=%s,str3=%s"%(str1,str2,str3)
    return HttpResponse("ok")