SQLAlchemy中的关系未按预期工作

Question

我试图在两个表之间创建关系：event和location。 我要做的就是建立一对多的关系。事件可以在一个位置给定，因此该位置必须能够容纳各种事件。我已经摆弄外键好几个小时了，我想不出如何使它工作。在

我的位置.py看起来像这样：

from datetime import datetime

from sqlalchemy import Column, Integer, ForeignKey, Float, Date, String
from sqlalchemy.orm import relationship

from model import Base

class Location(Base):
    __tablename__ = 'location'
    id = Column(Integer, primary_key=True, nullable=False)
    title = Column(String, unique=True)
    description = Column(String, nullable=False)
    founder_id = Column(Integer, ForeignKey('users.id'))
    latitude = Column(Float)
    longtitude = Column(Float)
    creation_date = Column(Date, default=datetime.now)


    # Relationships
    creator = relationship('User', foreign_keys=founder_id)
    events = relationship('Event', back_populates='location')

以及事件.py看起来像这样：

^{pr2}$

我从sqlalchemy得到的stactrace如下所示：

sqlalchemy.exc.InvalidRequestError: One or more mappers failed to initialize - can't proceed with initialization of other mappers. Triggering mapper: 'Mapper|Location|location'. Original exception was: Could not determine join condition between parent/child tables on relationship Location.events - there are no foreign keys linking these tables. Ensure that referencing columns are associated with a ForeignKey or ForeignKeyConstraint, or specify a 'primaryjoin' expression.

我真的很困惑，也不明白为什么这种一对多应该有效。在

Answer 1

Event需要一个指向Location的ForeignKey来构造关系。具体地说，您希望更改Event.location_id的定义，以添加ForeignKey('location.id')（并去掉后面的逗号；Event.location_id当前是一个元组）。在