python3&;Django Rest框架-如何查询M-1-M模型?
我有这些模型:python3&;Django Rest框架-如何查询M-1-M模型?,python,django,django-rest-framework,model,django-queryset,Python,Django,Django Rest Framework,Model,Django Queryset,我有这些模型: 组织机构 学生 课程 招生 学生属于某个组织 学生可以注册一门或多门课程 因此,注册记录基本上由给定的课程和给定的学生组成 class Organisation(TimeStampedModel): objects = models.Manager() name = models.CharField(max_length=50) def __str__(self): return self.name class Student(TimeStampedM
- 组织机构
- 学生
- 课程
- 招生
class Organisation(TimeStampedModel):
objects = models.Manager()
name = models.CharField(max_length=50)
def __str__(self):
return self.name
class Student(TimeStampedModel):
objects = models.Manager()
first_name = models.CharField(max_length=50)
last_name = models.CharField(max_length=50)
email = models.EmailField(unique=True)
organisation = models.ForeignKey(to=Organisation, on_delete=models.SET_NULL, default=None, null=True)
def __str__(self):
return self.email
class Course(TimeStampedModel):
objects = models.Manager()
language = models.CharField(max_length=30)
level = models.CharField(max_length=2)
def __str__(self):
return self.language + ' ' + self.level
class Meta:
unique_together = ("language", "level")
class Enrollment(TimeStampedModel):
objects = models.Manager()
course = models.ForeignKey(to=Course, on_delete=models.CASCADE, default=None, null=False)
student = models.ForeignKey(to=Student, on_delete=models.CASCADE, default=None, null=False)
enrolled = models.DateTimeField()
last_booking = models.DateTimeField()
credits_total = models.SmallIntegerField(default=10)
credits_balance = models.DecimalField(max_digits=5, decimal_places=2)
如果有一个组织ID,我知道我可以为一个学生注册,如下所示:
o=Organisation.objects.get(id=1)
o.student_set.all()[0].enrollment_set.all()
但如何检索给定组织的所有注册
例如,如果我想数一数某个组织有多少学生注册了课程?大概是这样的:
o.student_set.enrollment_set.count()
您可以使用以下命令反向查询:
Enrollment.objects.filter(student__organisation=o).count()
Enrollment.objects.filter(student__organisation__id=1).count()