SQLAlchemy ORM仅加载具有多个连接的列[重复]

Question

这个问题在这里已有答案：

• Flask SQLAlchemy query, specify column names 5个答案
• querying and selecting specific column in SQLAlchemy 1回答

我现在有：

class DeviceModel(db.Model):

    id = db.Column(db.Integer, primary_key=True)
    vendor = db.Column(db.String, nullable=False)
    model = db.Column(db.String, nullable=False)
    group_id = db.Column(db.ForeignKey('device_group.id', ondelete='SET NULL'), nullable=True)

class DeviceGroup(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String, nullable=False, unique=True)
    device_type_id = db.Column(db.ForeignKey('device_type.id', ondelete='SET NULL'), nullable=True)
    device_type = db.relationship("DeviceType", lazy='joined')

class DeviceType(db.Model):

    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String, nullable=False, unique=True)

我怎么才能查询DeviceModel.id，DeviceType.name字段？

在纯sql中它是：

SELECT device_model.id               AS device_model_id,
       device_type_1.name            AS device_type_1_name
FROM device_model
       LEFT OUTER JOIN device_group AS device_group_1 ON device_group_1.id = device_model.group_id
       LEFT OUTER JOIN device_type AS device_type_1 ON device_type_1.id = device_group_1.device_type_id;

Answer 1

一杯茶创造了魔力，我回答自己

records = db.session.query(DeviceModel.id,DeviceType.name).join(DeviceGroup).join(DeviceType).all()