Question

我是Django的新手，我正在尝试创建一个网站来管理班级信息，例如学生及其统计信息。当我单击一个班级时，我可以看到该班级的详细信息以及该班级的学生。但是，我也希望获得每个学生的平均分数，但是我不知道如何从我的统计模型中检索数据。我尝试了select_related但没有用。预先谢谢你。

我想在Django中做到这一点

SELECT class.id, class.name, class.day_and_time, student.name, average(statistics.dictation_score), average(statistics.grammar_score)
FROM classes
INNER JOIN students on student_class = class.id
INNER JOIN statistics on student = student.id
WHERE class.id =(some number)

我的模型.py文件：

class Classes(models.Model):
    name = models.CharField(max_length=256)
    day_and_time= models.CharField(max_length=256)

    def __str__(self):
        return self.name

    def get_absolute_url(self):
        return reverse("classesapp:class_detail", kwargs={"pk": self.pk})


class Students(models.Model):
    name = models.CharField(max_length=256)
    student_class =  models.ForeignKey(
        Classes, related_name = 'students', on_delete=models.SET_NULL, null=True
    )

    def __str__(self):
        return self.name

    def get_absolute_url(self):
        return reverse("classesapp:student_detail", kwargs={"pk": self.pk})

class Statistics(models.Model):
    student= models.ForeignKey(
        Students, related_name='statistics', on_delete=models.CASCADE, null=True
    )
    date = models.DateField(blank=True, null=True)
    dictation_score = models.FloatField()
    writing_score = models.FloatField()
    test_score = models.FloatField()
    grammar_score = models.FloatField()
    in_class_performance = models.FloatField()

    class Meta:
        ordering = ["-date"]

    def get_absolute_url(self):
        return reverse("classesapp:classes_list")

我的观点.py文件：

class ClassesDetailView(DetailView):
    stats  = models.Students.objects.select_related('statistics')
    context_object_name = "class_detail"
    model = models.Classes
    template_name = "classesapp/class_detail.html"

我想做什么： Image from the site what I want to do

如何从相关模型中检索数据？

0 个答案: