title: In SQL Alchemy, how do I include a field from a joined table in fields list?
body: <p>Take these table definitions:</p>
  
  <pre><code>class Device(Base):
      __tablename__ = 'devices'
  
      id = Column(Integer, primary_key = True)
      imei = Column(String(19))
  
  class Position(Base):
      __tablename__ = 'positions'
  
      id = Column(Integer, primary_key = True)
      device_id = Column(Integer, ForeignKey('devices.id'))
      latitude = Column(Float(8))
      longitude = Column(Float(8))
      other = Column(String(512))
  
      device = relationship('Device', foreign_keys = [device_id])
  </code></pre>
  
  <p>I can query for specific fields of a position like this:</p>
  
  <pre><code>&gt;&gt;&gt; pos = session.query(Position.latitude, Position.longitude).first()
  &gt;&gt;&gt; pos
  (-22.929775, -43.23409)
  &gt;&gt;&gt;
  </code></pre>
  
  <p>I can get long, lat and imei like this:</p>
  
  <pre><code>&gt;&gt;&gt; pos = session.query(Position).first()
  &gt;&gt;&gt; pos.latitude, pos.longitude, pos.device.imei
  (-22.929775, -43.23409, '123456789')
  &gt;&gt;&gt;
  </code></pre>
  
  <p>How can I query for latitude, longitude and device.imei (like in 1st example) without having to select all other data that comes with it (like in 2nd example)?</p>