Question

我在Peewee中有两个查询，第一个查询返回一个与最小值和最大值匹配的捐赠表，然后乘以一个因子。另一笔将退回所有超出最小/最大范围的捐款。它们运行之后，我使用UNION ALL运算符获得了一组组合的结果：

database.execute_sql('PRAGMA foreign_keys = ON;')
with database.transaction():
    # part multiplied by factor
    query1 =  (Donation
                .select(Donation.donor.alias('donor'),
                        fn.SUM((Donation.amount)*factor).alias('total'))
                .where(
                        (Donation.amount > min_donation) &
                        (Donation.amount < max_donation)
                        )
                .group_by(Donation.donor)
                )
    query2 =  (Donation
                .select(Donation.donor.alias('donor'),
                        (fn.SUM(Donation.amount)).alias('total'))
                .where(
                        #(Donation.amount <= min_donation) &
                        (Donation.amount >= max_donation)
                        )
                .group_by(Donation.donor)
                )

    query = ((query1 + query2)
                .select(
                    SQL('donor'),
                    fn.SUM(SQL('total'))
                )
                .group_by(SQL('donor'))
                .order_by(SQL('donor'))
        )

它现在的编码方式，它抱怨我无法在组合查询中选择：

Traceback (most recent call last):
  File "run_mailroom_db.py", line 350, in project
    for i in query:
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/peewee.py", line 1611, in __iter__
    self._ensure_execution()
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/peewee.py", line 1607, in _ensure_execution
    raise ValueError('Query has not been executed.')

现在，我的问题是，是否有一种方法可以从组合查询中提取单个列，并像返回数据库表一样执行返回分组值的SUM之类的事情？

Answer 1

在实现了此处提出的解决方案之后，这是更新的代码：

database.execute_sql('PRAGMA foreign_keys = ON;')
with database.transaction():
    # part multiplied by factor
    query1 =  (Donation
                .select(Donation.donor.alias('donor'),
                        fn.SUM((Donation.amount)*factor).alias('total'))
                .where(
                        (Donation.amount > min_donation) &
                        (Donation.amount < max_donation)
                        )
                .group_by(Donation.donor)
                )
    query2 =  (Donation
                .select(Donation.donor.alias('donor'),
                        (fn.SUM(Donation.amount)).alias('total'))
                .where(
                        (Donation.amount <= min_donation) |
                        (Donation.amount >= max_donation)
                        )
                .group_by(Donation.donor)
                )

    query = ((query1 + query2)
                .select(
                    SQL('donor'),
                    fn.SUM(SQL('total'))
                )
                .group_by(SQL('donor'))
                .order_by(SQL('donor'))
        )

    pp.pprint("="*60)
    pp.pprint("Projected Donors for factor: {}, min: {}, max: {}".format(factor,
                                                                min_donation,
                                                                max_donation)
            )
    pp.pprint('{:30} | {:30}'.format(
                            'Donor',
                            'Total'))
    pp.pprint("="*60)
    for i in query.execute(database):
        pp.pprint("{:30} | {:30}".format(str(i['donor']),
                                            str(i['SUM(total)'])
                                    )
                        )

从Peewee中的组合查询中选择列

1 个答案: