Question

我确实有这两个calsses als DB模型试图建立一对多的关系：

class User(db.Model):
    __tablename__ = 'users'
    id = db.Column(db.Integer, primary_key=True)
    email = db.Column(db.String(255), index=True) #, unique=True)
    firstname = db.Column(db.String(50))
    lastname = db.Column(db.String(50))

    bt_ids = db.relationship("BT", order_by="BT.id", backref="user")



class BT(db.Model):
    __tablename__ = 'bt'
    id = db.Column(db.Integer, primary_key=True)
    bt_id = db.Column(db.String(255), unique=True)
    user_id = db.Column(db.Integer, db.ForeignKey('users.id'))

    user = db.relationship("User", backref=db.backref('bt', order_by=id))

但我想我并不真正理解建立关系的方式：

ArgumentError: Error creating backref 'user' on relationship 'User.bt_ids': property of that name exists on mapper 'Mapper|BT|bt'

有什么想法吗？

编辑

我其实想要获得类似SQLAlchemy

的例子

class User(Base):
    __tablename__ = 'users'
    id = Column(Integer, Sequence('user_id_seq'), primary_key=True)
    name = Column(String(50))
    fullname = Column(String(50))
    password = Column(String(12))

    **addresses = relationship("Address", order_by="Address.id", backref="user")**

    def __repr__(self):
        return "<User(name='%s', fullname='%s', password='%s')>" % (
                                self.name, self.fullname, self.password)



class Address(Base):
     __tablename__ = 'addresses'
     id = Column(Integer, primary_key=True)
     email_address = Column(String, nullable=False)
     user_id = Column(Integer, ForeignKey('users.id'))

     **user = relationship("User", backref=backref('addresses', order_by=id))**

     def __repr__(self):
         return "<Address(email_address='%s')>" % self.email_address

Answer 1

FK和User到BT属性之间已存在user_id关系，因此您无法在BT中创建另一个名为user的关系

class User(db.Model):
    __tablename__ = 'users'
    id = db.Column(db.Integer, primary_key=True)
    email = db.Column(db.String(255), index=True) #, unique=True)
    firstname = db.Column(db.String(50))
    lastname = db.Column(db.String(50))
    bts = db.relationship("BT", order_by="BT.id", backref="user")

class BT(db.Model):
    __tablename__ = 'bt'
    id = db.Column(db.Integer, primary_key=True)
    bt_id = db.Column(db.String(255), unique=True)
    user_id = db.Column(db.Integer, db.ForeignKey('users.id'))

Answer 2

现在我明白了......

这是错的：

user = db.relationship（＆＃34; User＆＃34;，backref = db.backref（＆＃39; bt_ids ＆＃39;，order_by = id））

现在有效！

SQLAlchemy关系错误

2 个答案: