循序渐进Python3（十）-- 3 -- SqlAlchemy

使用sqlalchemy 创建外键关联

class Host(Base):
    __tablename__ = 'host'
    id = Column(Integer, primary_key=True, autoincrement=True)
    host_name = Column(String(64), nullable=False)
    ip_addr = Column(String(128), unique=True, nullable=False)
    port = Column(Integer, default=22)
    host_user = Column(String(64), nullable=False)
    host_pw = Column(String(64), nullable=False)

class Work(Base):
    __tablename__ = 'work'  # 实际创建的表名
    id = Column(Integer, primary_key=True, autoincrement=True)
    work_name = Column(String(64),  unique=True, nullable=False)

class HostWork(Base):
    __tablename__ = 'hostwork'
    id = Column(Integer, primary_key=True, autoincrement=True)
    host_id = Column(Integer, ForeignKey('host.id'))
    work_id = Column(Integer, ForeignKey('work.id'))
    host_info = relationship("Host", backref="hostinfo")
    work_info = relationship("Work", backref="workinfo")

通过含有relationship的表去查找相关联的表 叫正向查找；

反之，则叫反向查找；

看个例子：

# 利用relationship先反向查找 “操作类型和主机id” 在正向查找主机详细信息
works = new_session.query(init_db.Work).filter(init_db.Work.work_name == work_type[0]).first()
for item in works.workinfo:
    print(item.host_info.host_name)

来自为知笔记(Wiz)