SQLAlcehmy - 无法确定要加入哪个 FROM 子句

Question

我有 3 个模型，我需要它们的一些列：class candidates(db.Model):    id = db.Column(db.Integer, primary_key = True, autoincrement=True, nullable=False)    name = db.Column(db.String(50), nullable= False)    surname = db.Column(db.String(50), nullable= False)    father_name = db.Column(db.String(50), nullable= False)        class students(db.Model):    id = db.Column(db.Integer, primary_key = True, autoincrement=True, nullable=False)    candidate_id = db.Column(db.Integer, db.ForeignKey('candidates.id'), nullable= False) # Foreign key to Candidates       type = db.Column(db.Integer, nullable= False)     family_status = db.Column(db.Boolean(), nullable= False)    education_status = db.Column(db.Boolean(), nullable= False)class graduate_students(db.Model):    id = db.Column(db.Integer, primary_key = True, autoincrement=True, nullable=False)    student_id = db.Column(db.Integer, db.ForeignKey('students.id'), nullable= False)     work_place = db.Column(db.String(255), nullable= False)    salary = db.Column(db.Integer, nullable= False)result = graduate_students.query.with_entities(    graduate_students.id, students.id,     candidates.id, candidates.name, candidates.surname).join(students).join(candidates).all()print(result)但解释器给了我这个错误：“无法确定要加入哪个 FROM 子句” sqlalchemy.exc.InvalidRequestError：无法确定要从哪个 FROM 子句加入，有多个 FROM 可以加入到该实体。请使用 .select_from() 方法建立显式左侧，并提供显式 ON 子句（如果尚不存在）以帮助解决歧义。

Answer 1

if request.method == "POST":

        form = QuestionForm(request.POST or None)

        if form.is_valid():

            new_question = form.save()  

            student = Student.objects.get(user = request.user)

            new_question.student = student

            new_question.save()

            if((len(request.FILES) =