Question

我正在努力解决一些简单的问题，我想通过过滤关系类键来查找对象。

我有以下课程（简体）：

Hub --has_many-> Room --has_many--> Sensor --has_many-->Measurement

简化版


class Hub(Base):
    __tablename__ = 'hubs'
    id           = Column(Integer, primary_key=True,autoincrement=True)
    hub_name     = Column(String(120), primary_key=True)
    rooms        = relationship(ROOM_CL, backref="hub",lazy='dynamic')

class Room(Base):
    __tablename__ = 'rooms'
    id            = Column(Integer, primary_key=True,autoincrement=True)
    room_name     = Column(String(120), primary_key=True)
    hub_id        = Column(Integer, ForeignKey(Hub.getTable()+'.id'), primary_key=True)
    sensors       = relationship(SENSOR_CL, backref="room",lazy='dynamic')

class Sensor(Base):
    __tablename__ = 'sensors'
    id            = Column(Integer, primary_key=True,autoincrement=True)
    sensor_name   = Column(String(120), primary_key=True)
    room_id       = Column(Integer, ForeignKey(Room.getTable()+'.id'), primary_key=True)
    measurements  = relationship(MEAS_CL, backref="sensor",lazy='dynamic')

class Measurement(Base):
    __tablename__ = 'measurements'
    id             = Column(Integer, primary_key=True,autoincrement=True)
    date_time      = Column(DateTime)
    sensor_id      = Column(Integer, ForeignKey(Sensor.getTable()+'.id'), primary_key=True)
    value          = Column(Float)

现在想像我已经获得

hub_name    = 'Hub1'
room_name   = 'livingroom'
sensor_name = 'pir1'

我想找到所需传感器的所有测量值。我知道我可以分层：

mhub = self.sqlsession.query(Hub).filter(Hub.hub_name=='Hub1').first()
mroom = mhub.rooms.filter(Room.room_name=='livingroom').first()
msensor = mroom.sensors.filter(Sensor.sensor_name=='pir1').first()
mmeas = msensor.measurements

但这对我来说似乎是一个丑陋的解决方案。由于我已经拥有所有主键，因此可以过滤

之类的东西

mmeas = self.sqlsession.query(Measurement).filter(Sensor.sensor_name=='pir1',Room.room_name=='livingroom',Hub.hub_name=='Hub1').all()

尝试过，但是它给了我表格中的所有结果

我认为我在某个时候误解了这个概念，而且我做错了方法。感谢您的帮助！

SQLalchemy按关系类属性过滤

0 个答案: