Sqlalchemy

Question

我有以下型号。

class Customer(db.Model):
id = db.Column(db.Integer, db.ForeignKey('accounts.id'), primary_key=True)
firstname = db.Column(db.Unicode(128), index=True)
lastname = db.Column(db.Unicode(128), index=True)
account = db.relationship('Account',
                backref=db.backref('customer',
                            uselist=False,
                            cascade=DEFAULT_WITH_DELETE_CASCADE),
                single_parent=True,
                cascade=DEFAULT_WITH_DELETE_CASCADE,
                foreign_keys=[id])

我想在加载客户时对帐户进行 eagarloading table。我将更多过滤器和连接应用于查询，然后希望按 Customer.id 对结果进行分组，以便为客户获得独特的结果。

query = Customer.query.join(Customer.account).options(joinedload(Customer.account))
query = query.order_by(Account.registered_on.desc()).group_by(Customer.id, Account.id)

但是当我在 joinloaded 后使用 group_by 子句时，我得到了错误。 joinloaded后如何使用group_by？

ProgrammingError: (ProgrammingError) column "accounts_1.id" must appear in the GROUP BY clause or be used in an aggregate function

Answer 1

我认为您不能按您加入的 table 中的列分组（使用 joinedload）。来自 SQLAlchemy 文档：The joins produced by orm.joinedload() are anonymously aliased. The criteria by which the join proceeds cannot be modified, nor can the Query refer to these joins in any way, including ordering. (http://docs.sqlalchemy.org/en/latest/orm/loading_relationships.html)

您需要在此处使用常规 join 函数，然后 group_by

Sqlalchemy - 加入后分组

Sqlalchemy - group by after joinloaded

flask

flask-sqlalchemy