Django 模型一對一，一對多，多對多的正反查詢

• 先上示例模型
  • 一對一的情況

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')

• • 一對多的情況

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') 這里的 a ☞ related_name='a'

沒有related_name屬性時
b_id = A.objects.get(id=1).b_set.all().values()   采用類名小寫_set的方式

• • 多對多的情況

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屬性類似上面

 隨手記錄，不足之處請多指教！！！