Question

我正在尝试在我的python应用程序上使用SQLAlchemy，但我遇到了多对多关系的问题。我有4张桌子：

用户，标志，指挥官，频道和commandes_channels_flags

commandes_channels_flags包含每个相关表的外键（commandes，channels和flags）

用户也将flag_id作为外键。

所以我尝试链接commandes，channels和flag。目标是知道一个命令可以在一个标志的通道上运行。

我这样做了：

from sqlalchemy import Column, Integer, String, ForeignKey
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import relationship

Base = declarative_base()


class User(Base):
    __tablename__ = 'users'

    id = Column(Integer, primary_key=True)
    pseudo = Column(String(50), unique=True, nullable=False)
    flag_id = Column(ForeignKey('flags.id'))


class Flag(Base):
    __tablename__ = 'flags'

    id = Column(Integer, primary_key=True)
    irc_flag = Column(Integer)
    nom = Column(String(50))

    users = relationship("User", backref="flag", order_by="Flag.irc_flag")
    commande = relationship("Commande", secondary="commandes_channels_flags", back_populates="flags")
    channel = relationship("Channel", secondary="commandes_channels_flags", back_populates="flags")


class Channel(Base):
    __tablename__ = 'channels'

    id = Column(Integer, primary_key=True)
    uri = Column(String(50))
    topic = Column(String(255))

    commande = relationship("Commande", secondary="commandes_channels_flags", back_populates="channels")
    flag = relationship("Flag", secondary="commandes_channels_flags", back_populates="channels")


class Commande(Base):
    __tablename__ = 'commandes'

    id = Column(Integer, primary_key=True)
    pattern = Column(String(50))

    channel = relationship("Channel", secondary="commandes_channels_flags", back_populates="commandes")
    flag = relationship("Flag", secondary="commandes_channels_flags", back_populates="commandes")


class CommandeChannelFlag(Base):
    __tablename__ = 'commandes_channels_flags'

    id = Column(Integer, primary_key=True)
    commande_id = Column(ForeignKey('commandes.id'))
    channel_id = Column(ForeignKey('channels.id'))
    flag_id = Column(ForeignKey('flags.id'))

但我有这个错误：

sqlalchemy.exc.InvalidRequestError: Mapper 'Mapper|Commande|commandes' has no property 'channels'

我知道我的表链接有错误，但我找不到它。

Answer 1

back_populates需要匹配其他模型上相关属性的确切名称。在Channel，您有back_populates="channels"，但在Commande，您有：{/ p>

channel = relationship("Channel", secondary="commandes_channels_flags", back_populates="commandes")

相反，请将channel = relationship更改为channels = relationship。

您还需要将其他关系属性更改为Flag.commandes，Flag.channels，Channel.commandes，Channel.flags和Commande.flags以匹配您的{{ 1}}参数。

使用SqlAlchemy加入条件时出错

1 个答案: