官方关于一对多和多对多的映射：https://flask-sqlalchemy.palletsprojects.com/en/2.x/models/#many-to-many-relationships
我的案例：
一个Wallet 对应多张表【BuyOrder和OrderBase】
class Wallet(Base):
# 每条wallet记录对应多条buy_order相同的记录
buy_order = db.relationship("BuyOrder", backref='wallet', lazy=True)
# 每条wallet记录对应多条sell_order相同的记录
sell_order = db.relationship("SellOrder", backref='wallet', lazy=True)
# 与wallet关联
class BuyOrder(OrderBase):
address = db.Column(db.String(255), db.ForeignKey('wallet.address'), nullable=False)
# 与wallet关联
class SellOrder(OrderBase):
address = db.Column(db.String(255), db.ForeignKey('wallet.address'), nullable=False)