如何从一个喜欢的表格中获取数据，该表格喜欢另一个自己喜欢的表格？

Question

我有三个表，result，course，study，如下所示

class Study(models.Model):
    id_study = models.IntegerField(primary_key=True)
    study_name = models.CharField(max_length=45)
    description = models.CharField(max_length=45, blank=True, null=True)
    language = models.CharField(max_length=45)
    number_of_years = models.CharField(max_length=45)

class Course(models.Model):
    id_course = models.AutoField(primary_key=True)
    course_name = models.CharField(max_length=45, blank=True, null=True)
    description = models.CharField(max_length=45, blank=True, null=True)
    credits = models.CharField(max_length=45, blank=True, null=True)
    teacher_id_teacher = models.ForeignKey('Teacher', models.DO_NOTHING, db_column='teacher_id_teacher')
    study_id_study = models.ForeignKey('Study', models.DO_NOTHING, db_column='study_id_study')

class Exam(models.Model):
    id_exam = models.AutoField(primary_key=True)
    room = models.CharField(max_length=45, blank=True, null=True)
    resit = models.CharField(max_length=45, blank=True, null=True)
    date = models.DateField(blank=True, null=True)
    time = models.TimeField(blank=True, null=True)
    course_id_course = models.ForeignKey(Course, models.DO_NOTHING, db_column='course_id_course')


class Result(models.Model):
    id_result = models.AutoField(primary_key=True)
    grade = models.IntegerField(blank=True, null=True)
    exam_id_exam = models.ForeignKey(Exam, models.DO_NOTHING, db_column='exam_id_exam')
    date = models.DateField(blank=True, null=True)
    student_id_student = models.ForeignKey('Student', models.DO_NOTHING, db_column='student_id_student')
    passed = models.CharField(max_length=45, blank=True, null=True)

我想根据我给出的 study_id 得到一个结果对象

成绩取决于考试，考试取决于课程，课程取决于学习

提前致谢

Answer 1

您可以使用双下划线表示法在查询中跟踪关系

Result.objects.filter(
    exam_id_exam__course_id_course__study_id_study__id=study_id
)

对于它的价值：你的外键有一个奇怪的命名约定，通常一个名为 Exam 的模型的外键将被命名为 exam，你已经为每个外键设置了 db_column，所以你不需要以这种方式命名它们。如果您将它们的名称更改为模型名称小写，它看起来像这样，可能更具可读性

Result.objects.filter(exam__course__study__id=study_id)