SQLAlchemy - 无法确定要加入哪个 FROM 子句

Question

我有 3 个模型，我需要它们中的一些列：

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)

但是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：无法确定从哪个 FROM 子句加入，有多个 FROM 可以加入该实体。请使用 .select_from() 方法来建立显式左侧，并提供一个显式 ON 子句（如果尚未存在）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) =