SqlAlchemy

Question

目前我使用的查询如下：

Model.query.with_entities(Model.m_t,
                    func.sum(Model.a),func.sum(Model.b),
                    func.sum(Model.c),func.sum(Model.d),
                    func.sum(Model.f)).group_by(Model.g).\
                    filter(*queries).paginate(page_number, page_size, False
                    )

尽管这按预期工作，但如您所见，如果列数增加（for func sum），代码会变得重复。搜索了一段时间后，我想到了这个：

col_headers = ["a", "b", "c", "d", "f"]
search_columns = [getattr(Model, i) for i in col_headers]
Model.query.with_entities(Model.m_t,
                         func.sum(*search_columns)).group_by(Model.g).\
                         filter(*queries).paginate(page_number, page_size, False
                         )

但这并不像预期的那样有效。我收到以下错误

can't adapt type 'InstrumentedAttribute' Exception as not enough values to unpack (expected 3, got 2)

我知道我漏掉了一些小东西。感谢您的帮助！

Answer 1

您应该将 sum 分别应用于每一列：

search_columns = [db.func.sum(getattr(Model, i)) for i in col_headers]

您可以使用Query.add_columns向查询结果添加列：

query = query.add_columns(*search_columns)

或者您可以直接传递它们：

Model.query.with_entities(Model.m_t, *search_columns)

综合起来：

col_headers = ["a", "b", "c", "d", "f"]
search_columns = [db.func.sum(getattr(Model, i)) for i in col_headers]
query = (
    Model.query.with_entities(Model.m_t, *search_columns)
    .group_by(Model.g)
    .filter(*queries)
    .paginate(page_number, page_size, False)
)

SqlAlchemy - func sum 的多列

SqlAlchemy - Multiple Columns for func sum

python

flask-sqlalchemy