Django 模型一对一，一对多，多对多的正反查询

• 先上示例模型
  • 一对一的情况

class A(models.Model):
    name = models.CharField(max_length=30, blank=True)
    ida = models.CharFileld(max_length=30, blank=True)

class B(models.Model):
    name = models.CharField(max_length=30, blank=True)
    idb = models.CharField(max_length=30, blank=True)
    a = models.OneToOneField(to="A", on_delete=models.CASCADE，related_name='a')

a_queryset = A.objects.get(id=1)
b = a_queryset.b
b_queryset = B.objects.get(id=1)
a = b_queryset.a

or

ida = A.objects.filter(id=1).values('a__ida', 'name')

• • 一对多的情况

class A(models.Model):
    name = models.CharField(max_length=30, blank=True)
    ida = models.CharFileld(max_length=30, blank=True)

class B(models.Model):
    name = models.CharField(max_length=30, blank=True)
    idb = models.CharField(max_length=30, blank=True)
    a = models.ForeignKey(to="A", on_delete=models.CASCADE，related_name='a')

正查
a_id = B.objects.get(id=1).a
反查
b_id= A.objects.get(id=1).a.all().values()
idb= A.objects.filter(id=1).values('a__idb') 这里的 a ☞ related_name='a'

没有related_name属性时
b_id = A.objects.get(id=1).b_set.all().values()   采用类名小写_set的方式

• • 多对多的情况

class A(models.Model):
    name = models.CharField(max_length=30, blank=True)
    ida = models.CharFileld(max_length=30, blank=True)

class B(models.Model):
    name = models.CharField(max_length=30, blank=True)
    idb = models.CharField(max_length=30, blank=True)
    a = models.ManyToManyField(to="A")

b= B.objects.get(nid='1')
a= b.a.all()

a= A.objects.get(id='1')
b= a.b_set.all()  有related_name属性类似上面

 随手记录，不足之处请多指教！！！