Question

我正在使用flask-sqlalchemy实现多对多关系。尝试了许多选项，但无法查询所有孩子的父母。

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在此多对多关系示例中，我将如何查询参与者参加的所有比赛？

我尝试了以下操作：

class Participant(db.Model):
    __tablename__='participant'
    __table_args__ = {'extend_existing': True} 

    id = db.Column(db.Integer, primary_key=True)
    email = db.Column(db.String(120), unique=True)
    name = db.Column(db.String(120), unique=False)

    user_id = db.Column(db.Integer, db.ForeignKey('user.id'))
    user = db.relationship("User")

    @staticmethod
    def get_by_user(user):
        return Participant.query.filter_by(user=user).first()

    def __repr__(self):
        return "(Participant '{}')".format(self.email)

    competitions = db.relationship("CompetitionParticipant", back_populates="participant")

class Competition(db.Model): 
    __tablename__='competition'
    __table_args__={'extend_existing':True}

    id=db.Column(db.Integer,primary_key=True)

    name=db.Column(db.String(100),unique=True)
    description=db.Column(db.String(255),unique=True)
    # type=db.Column(db.String(50))#Team,Individual,Practice,etc.
    start_date=db.Column(db.DateTime)
    end_date=db.Column(db.DateTime)
    result_date=db.Column(db.DateTime)

    participants = db.relationship('CompetitionParticipant', back_populates='competition')

    def __repr__(self):
        return "(Competition '{}')".format(self.name)

class CompetitionParticipant(db.Model): 
    __tablename__='competition_participant'
    __table_args__={'extend_existing':True}

    id=db.Column(db.Integer,primary_key=True)
    participant_id=db.Column(db.Integer, db.ForeignKey('participant.id'))
    competition_id=db.Column(db.Integer, db.ForeignKey('competition.id'))

    competition=db.relationship("Competition",back_populates="participants")
    participant=db.relationship("Participant",back_populates="competitions")

    def __repr__(self):
        return "(competition_id, participant_id '{},{}')".format(self.competition_id,self.participant_id)

我尝试的所有其他操作都是语法错误。提取参与者参加的所有比赛的正确ORM方法是什么？

Answer 1

例如，如果您想获取特定用户的比赛数据：

participants = Participant.query.filter_by(id=1).all()

您可以遍历参与者并获取数据：

for participant in participants:
    for competition in participant.competitions:
        print(competition.competition.name)

Answer 2

如果您想了解有关id = 1的参与者的信息，您应该不能做这样的事情：

participant = Participant.query.get(1)
for item in participant.competitions:
       print(item.name)

多对多关系-如何查询所有孩子

2 个答案: