FastAPI 数据库多对多

参考: https://docs.sqlalchemy.org/en/14/orm/cascades.html#using-delete-cascade-with-many-to-many-relationships

级联删除，如果不级联删除，那么去除 cascade、ondelete

association_table = Table(
    "association",
    Base.metadata,
    Column("left_id", Integer, ForeignKey("left.id", ondelete="CASCADE")),
    Column("right_id", Integer, ForeignKey("right.id", ondelete="CASCADE")),
)


class Parent(Base):
    __tablename__ = "left"
    id = Column(Integer, primary_key=True)
    children = relationship(
        "Child",
        secondary=association_table,
        back_populates="parents",
        cascade="all, delete",
    )


class Child(Base):
    __tablename__ = "right"
    id = Column(Integer, primary_key=True)
    parents = relationship(
        "Parent",
        secondary=association_table,
        back_populates="children",
        passive_deletes=True,
    )