SQLAlchemy:如何在关系字段上排序查询结果(order_by)？

Question

楷模

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

BaseModel = declarative_base()

class Base(BaseModel):
   __tablename__ = 'base'
   id = Column(Integer, primary_key=True)
   location = Column(Unicode(12), ForeignKey("locationterrain.location"), unique=True,)
   name = Column(Unicode(45))
   ownerid =  Column(Integer,ForeignKey("player.id"))
   occupierid =  Column(Integer, ForeignKey("player.id"))
   submitid =  Column(Integer,ForeignKey("player.id"))
   updateid =  Column(Integer,ForeignKey("player.id"))
   owner = relationship("Player",
         primaryjoin='Base.ownerid==Player.id',
         join_depth=3,
         lazy='joined')
   occupier= relationship("Player",
         primaryjoin='Base.occupierid==Player.id',
         join_depth=3,
         lazy='joined')
   submitter = relationship("Player",
         primaryjoin='Base.submitid== Player.id',
         join_depth=3,
         lazy='joined')
   updater= relationship("Player",
         primaryjoin='Base.updateid== Player.id',
         join_depth=3,
         lazy='joined')


class Player(BaseModel):
   __tablename__ = 'player'
   id = Column(Integer, ForeignKey("guildmember.playerid"), primary_key=True)
   name =  Column(Unicode(45))

搜索

bases = dbsession.query(Base)
bases = bases.order_by(Base.owner.name)

这不起作用....我到处搜索并阅读文档.但我只是不知道如何根据他们的'所有者'关系的名称对我的(基本)查询进行排序.

它总是导致:

 AttributeError: Neither 'InstrumentedAttribute' object nor 'Comparator' object has an attribute 'name'

这一定很容易......但是我没有看到它.还查看了比较器,这似乎是合乎逻辑的,但我没有看到ORDER BY的查询部分在哪里生成或者我应该返回什么,因为所有内容都是动态生成的.为我的每个"玩家"关系制作一个比较器做一件简单的事情似乎过于复杂.

Answer 1

SQLAlchemy希望您从SQL的角度思考.如果你查询"Base",那就是:

SELECT * FROM base

简单.那么,在SQL中,你如何选择"base"中的行,并在一个完全不同的表中的"name"列中排序,即"player"？您使用加入:

SELECT base.* FROM base JOIN player ON base.ownerid=player.id ORDER BY player.name

SQLAlchemy让你使用相同的思维过程 - 你加入():

session.query(Base).join(Base.owner).order_by(Player.name)