Question

首先，数据库概述：

competitors - 参与竞争的人
competitions - 人们竞争的事情
competition_registrations - 参加特定比赛的参赛者
event - 比赛中的“赛事”。
events_couples - 一对（2名参赛者）参加比赛。

首先，EventCouple是一个与events_couples对应的Python类，它是：

class EventCouple(Base):
    __tablename__ = 'events_couples'

    competition_id = Column(Integer, ForeignKey('competitions.id'), primary_key=True)
    event_id = Column(Integer, ForeignKey('events.id'), primary_key=True)

    leader_id = Column(Integer)
    follower_id = Column(Integer)

    __table_args__ = (
        ForeignKeyConstraint(['competition_id', 'leader_id'], ['competition_registrations.competition_id', 'competition_registrations.competitor_id']),
        ForeignKeyConstraint(['competition_id', 'follower_id'], ['competition_registrations.competition_id', 'competition_registrations.competitor_id']),
        {}
    )

我有一个Python类CompetitorRegistration，它对应于competition_registrations中的记录/行。注册的竞争者可以参加多项赛事，但要么是“领导者”，要么是“追随者”。我想将CompetitorRegistration添加到leading属性EventCouple，这是competition_id和leader_id匹配的CompetitorRegistration列表。这是我的class CompetitorRegistration(Base): __tablename__ = 'competition_registrations' competition_id = Column(Integer, ForeignKey('competitions.id'), primary_key=True) competitor_id = Column(Integer, ForeignKey('competitors.id'), primary_key=True) email = Column(String(255)) affiliation_id = Column(Integer, ForeignKey('affiliation.id')) is_student = Column(Boolean) registered_time = Column(DateTime) leader_number = Column(Integer) leading = relationship('EventCouple', primaryjoin=and_('CompetitorRegistration.competition_id == EventCouple.competition_id', 'CompetitorRegistration.competitor_id == EventCouple.leader_id')) following = relationship('EventCouple', primaryjoin='CompetitorRegistration.competition_id == EventCouple.competition_id and CompetitorRegistration.competitor_id == EventCouple.follower_id')课程，完成了尝试：

ArgumentError: Could not determine relationship direction for primaryjoin
condition 'CompetitorRegistration.competition_id == EventCouple.competition_id
AND CompetitorRegistration.competitor_id == EventCouple.leader_id', on
relationship CompetitorRegistration.leading. Ensure that the referencing Column
objects have a ForeignKey present, or are otherwise part of a
ForeignKeyConstraint on their parent Table, or specify the foreign_keys parameter
to this relationship.

但是，我得到了：

following

感谢您的帮助，＆amp;如果模式需要更多信息，请告诉我。

另外，我的另一次尝试在competition_id中可见 - 这没有错误，但也没有给出正确的结果。（它只加入follower_id，完全忽略了{{1}}）

Answer 1

您的leading条件会将表达式和字符串混合为eval()。并且following的条件混合了Python和SQL运算符：Python中的and不是您所期望的。以下是使用两种变体的更正示例：

leading = relationship('EventCouple', primaryjoin=(
    (competition_id==EventCouple.competition_id) & \
    (competitor_id==EventCouple.leader_id)))

leading = relationship('EventCouple', primaryjoin=and_(
    competition_id==EventCouple.competition_id,
    competitor_id==EventCouple.leader_id))

following = relationship('EventCouple', primaryjoin=\
    '(CompetitorRegistration.competition_id==EventCouple.competition_id) '\
    '& (CompetitorRegistration.competitor_id==EventCouple.follower_id)')

帮助复杂的SQL Alchemy加入

1 个答案: