与ORM一起使用时的情况(SQLalchemy) [英] CASE WHEN with ORM (SQLalchemy)

问题描述

我将SQLAlchemy与ORM paragdim一起使用.我无法找到一种方法来进行CASE WHEN指令.我在网上找不到有关此信息.

I am using SQLAlchemy with the ORM paragdim. I don't manage to find a way to do a CASE WHEN instruction. I don't find info about this on the web.

有可能吗?

推荐答案

请参见

See sqlalchemy.sql.expression.case function and more examples on the documentation page. But it would look like this (verbatim from the documentation linked to):

case([(orderline.c.qty > 100, item.c.specialprice),
      (orderline.c.qty > 10, item.c.bulkprice)
    ], else_=item.c.regularprice)
case(value=emp.c.type, whens={
        'engineer': emp.c.salary * 1.1,
        'manager':  emp.c.salary * 3,
    })

编辑-1 :(回答评论)当然可以，请参见以下示例:

edit-1: (answering the comment) Sure you can, see example below:

class User(Base):
    __tablename__ = 'users'
    id = Column(Integer, primary_key=True, autoincrement=True)
    first_name = Column(String)
    last_name = Column(String)

xpr = case([(User.first_name != None, User.first_name + " " + User.last_name),],
        else_ = User.last_name).label("full_name")

qry = session.query(User.id, xpr)
for _usr in qry:
    print _usr.fullname

有关使用混合动力. >用于混合属性.

Also see Using a hybrid for an example of case used in the hybrid properties.

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