SQLAlchemy:使用自定义字段和值构建查询

时间:2014-04-03 11:34:01

标签: python sqlalchemy

如何将以下SQL查询转换为SQLAlchemy analog?

SELECT 'custom_value' AS `custom_field`, f.`bar` FROM `Foo` f

'Foo'模特:

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String

Base = declarative_base()

class Foo(Base):
    __tablename__ = 'Foo'

    id = Column(Integer, primary_key=True)
    bar = Column(String)

2 个答案:

答案 0 :(得分:2)

请看这个答案中的第二个例子:https://stackoverflow.com/a/3576573/344141

简而言之 - 使用literal("custom_value", type_=Unicode).label('custom_field'),因此您的查询将如下所示:

session.query(literal("custom_value", type_=Unicode).label('custom_field'), Foo.bar)

答案 1 :(得分:-2)

你需要做的是这样的事情:

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

Base = declarative_base()

class Foo(Base):
    __tablename__ = 'Foo'

    id = Column(Integer, primary_key=True)
    bar = Column(String)


engine = create_engine(connection_string, echo=False)
Session = sessionmaker(bind=engine)
db = Session()

# Results
qu = select([Foo.custom_field.label('custom_value'), Foo.bar])

results = db.query(qu).all()

[注意 - 我不接近Python的版本,但相信这是我的记忆中的正确