我有这些模型:
组织
学生
课程
注册
学生属于组织
一个学生可以注册一门或多门课程
因此,入学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(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 EnrollmentManager(models.Manager):
def org_student_count(self, organisation):
return self.filter(student__organisation__name="AEKI").count()
class Enrollment(TimeStampedModel):
objects = EnrollmentManager()
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)
考虑到组织ID,我知道我可以为一个学生注册,就像这样:
o=Organisation.objects.get(id=1)
o.student_set.all()[0].enrollment_set.all()
但是如何检索给定组织的所有注册?
例如,如果我想计算给定组织中有多少学生报名参加课程?像这样的东西:
o.student_set.enrollment_set.count()
您反向查询,带有: