A.ForeignKey B.OneToOneField C.ManyToOneField D.ManyToManyField
A.META B.REQUEST C.FILES D.Session
A.UserInfo.objects.get(username=xiaoming,sex=male) B.UserInfo.objects.get(username=xiaoming).get(sex=male) C.UserInfo.objects.filter(username=xiaoming,sex=male) D.UserInfo.objects.filter(username=xiaoming).filter(sex=male)