python - Django 查询 : Joining two models with two fields

Question

我有以下模型:

class AcademicRecord(models.Model):
    record_id = models.PositiveIntegerField(unique=True, primary_key=True)
    subjects = models.ManyToManyField(Subject,through='AcademicRecordSubject')
    ...


class AcademicRecordSubject(models.Model):
    academic_record = models.ForeignKey('AcademicRecord')
    subject = models.ForeignKey('Subject')
    language_group = IntegerCharField(max_length=2)
    ...


class SubjectTime(models.Model):
    time_id = models.CharField(max_length=128, unique=True, primary_key=True)
    subject = models.ForeignKey(Subject)
    language_group = IntegerCharField(max_length=2)
    ...


class Subject(models.Model):
    subject_id = models.PositiveIntegerField(unique=True,primary_key=True)
    ...

学术记录中有科目列表，每个科目都有一个语言代码，科目时间有一个科目和语言代码。

对于给定的 AcademicRecord，我如何才能获得与 AcademicRecord 具有的 AcademicRecordSubjects 相匹配的科目时间？

这是我的方法，但它会产生比需要更多的查询:

# record is the given AcademicRecord
times = []
for record_subject in record.academicrecordsubject_set.all():
    matched_times = SubjectTime.objects.filter(subject=record_subject.subject)
    current_times = matched_times.filter(language_group=record_subject.language_group)
    times.append(current_times)

我想使用 django ORM 而不是原始 SQL 进行查询

SubjectTime 语言组也必须与 Subject 的语言组匹配

Answer 1

我明白了，部分要感谢@Robert Jørgensgaard Eng

我的问题是如何使用超过 1 个字段进行内部联接，其中 F 对象派上了用场。
正确的查询是:

SubjectTime.objects.filter(subject__academicrecordsubject__academic_record=record,
                           subject__academicrecordsubject__language_group=F('language_group'))