Python SQLAlchemy ORM load_only具有多个联接的列
现在我有:Python SQLAlchemy ORM load_only具有多个联接的列,python,sqlalchemy,flask-sqlalchemy,Python,Sqlalchemy,Flask Sqlalchemy,现在我有: 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
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)
如何仅查询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;
“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()