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python - with_entities 指的是别名为

问题描述

这是原始问题的编辑版本，带有一个独立的示例。

from sqlalchemy import Column, Integer, String, create_engine, func
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

Base = declarative_base()


class User(Base):
    __tablename__ = 'users'
    id = Column(Integer, primary_key=True)
    name = Column(String)
    fullname = Column(String)
    nickname = Column(String)


engine = create_engine('sqlite://', echo=True)
Session = sessionmaker(bind=engine)
session = Session()
Base.metadata.create_all(engine)
session.add_all([
     User(name='wendy', fullname='Wendy Williams'),
     User(name='mary', fullname='Mary Contrary'),
     User(name='fred', fullname='Fred Flintstone', nickname='freddy')])

session.commit()

items = session.query(
       User.id, User.name,
       func.coalesce(User.nickname, 'Nicky').label('nickname'))

# Checking that with_entities works on original data set
subset_items = session.query(
       User.id, User.name)\
      .with_entities(User.name, User.nickname)\
      .all()
print(subset_items)

# items will be used elsewhere....
# Wanted: a subset with columns fullname and nickname only
# Result is wrong, it does not use coalesce result
special_items = items\
       .with_entities(User.fullname, User.nickname) \
       .all()
print(special_items)

如何使用 .with_entities 来引用项目？以下失败

.with_entities(items.fullname, items.nickname) \

@Nick 在回复原始问题时建议的带有引号的变体也是如此。

标签： pythonsqlitesqlalchemyflask-sqlalchemy

解决方案

由于没有回复，我将其发布在SQLAlchemy的社区网站上。答案出乎意料的尴尬：

q = q.with_entities(q.column_descriptions[1]['expr'], q.column_descriptions[2]['expr'])

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