SQLAlchemy:双OnetoOne关系声明

Question

对于我正在试验的数据库，建议我将Match和Team之间的关系从M2M改为两个1对1关系。逻辑是：每场比赛只有两个队。你知道吗

如何在我的models.py中实现这一点让我绞尽脑汁；以下是我目前得到的（节略）：

class Match(db.Model):
    id = db.Column(db.String, primary_key=True)


    # One to One x2 with Team
    hometeam_id = db.Column(db.Integer, db.ForeignKey('team.id'))
    awayteam_id = db.Column(db.Integer, db.ForeignKey('team.id'))
    team = db.relationship("Team", back_populates="match")

    hoemteam_goals = db.Column(db.Integer, nullable=False)
    awayteam_goals = db.Column(db.Integer, nullable=False)

class Team(db.Model):

    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String, nullable=False)
    points = db.Column(db.Integer)
    matches_played = db.Column(db.Integer)

    # Many side of M2M With Match
    match = relationship("Match", back_populates="team", uselist=False)

这里似乎缺少一些东西，特别是在relationship侧的Match声明中。你知道吗

Answer 1

解决方案是为每个一对一关系添加一个关系引用，并使用foreign_keys的relationship参数来指定要使用的id：

class Match(db.Model):
    id = db.Column(db.String, primary_key=True)

    # One to One x2 with Team
    hometeam_id = db.Column(db.Integer, db.ForeignKey('team.id'))
    awayteam_id = db.Column(db.Integer, db.ForeignKey('team.id'))
    hometeam = db.relationship("Team", foreign_keys=[hometeam_id])
    awayteam = db.relationship("Team", foreign_keys=[awayteam_id])

class Team(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String, nullable=False)
    points = db.Column(db.Integer)
    matches_played = db.Column(db.Integer)

    # No backreferences, use a query to figure that out

我删除了match关系，因为它在这里没有用，IMHO。你知道吗

相关文档如下：http://docs.sqlalchemy.org/en/latest/orm/join_conditions.html#relationship-foreign-keys