使用每列的选择性聚合从两列创建 SQL 值

Question

我有以下四个表： region_reference、community_grants、HealthWorkers 和 currency_exchange

和以下有效的 SQL 查询：

SELECT HealthWorkers.worker_id
  , community_grants.percentage_price_adjustment
  , community_grants.payment_status
  , community_grants.chosen
  , (region_reference.base_price * currency_exchange.euro_value) AS price
FROM currency_exchange 
  INNER JOIN (
    region_reference INNER JOIN (
      HealthWorkers INNER JOIN community_grants 
        ON HealthWorkers.worker_id = community_grants.worker_id
    ) ON (
      region_reference.community_id = community_grants.community_id
    ) AND (region_reference.region_id = community_grants.region_id)
  ) 
ON currency_exchange.currency = HealthWorkers.preferred_currency
WHERE (
  HealthWorkers.worker_id="malawi_01" 
    AND community_grants.chosen=True
);

它给了我以下结果集：

但是，我的任务是创建一个仅包含 4 个值的实体。

type OverallPriceSummary struct {
    Worker_id          string         `json:"worker_id"`
    Total_paid        decimal.Decimal `json:"total_paid"`
    Total_pledged     decimal.Decimal `json:"total_pledged"`
    Total_outstanding decimal.Decimal `json:"total_outstanding"`
}

Total_paid 是指定 worker_id 的值的总和，其中 payment_status = “1”（所有记录的总和）

Total_outstanding 是值的总和，其中 payment_status 为“0”且选择为真（所有记录合并）

Total_pledged 是 Total_paid 和 Total_outstanding 的总和（也是所有记录的总和）

我目前通过在我的代码中手动聚合这些值来获得这些值，因为 postgresql 遍历结果集，但我相信有一种方法可以避免这个临时 SQL 查询并从单个 SQL查询。我怀疑它涉及使用 SUM AS 和内部查询，但我不知道如何将它们组合在一起。任何帮助或指导将不胜感激。

编辑： 我在下面提供了一些示例数据：

region_reference

region_id	region_name	base_price	community_id
1	Lilongwe	100	19
2	Mzuzu	50	19

卫生工作者

worker_id	worker_name	preferred_currency	billing_address	charity_logo
malawi_01	Raphael Salanga	EUR	Nkhunga Health Centre in Nkhotakota District	12345

community_grants

region_id	campaign_id	worker_id	percentage_price_adjustment	community_id	payment_status	chosen	paid_price
1	1	malawi_01	10	19	0	Yes	0
2	1	malawi_01	0	19	1	Yes	20
3	1	malawi_01	1	19	0	Yes	0
1	1	malawi_01	0	23	0	Yes	30

currency_exchange

currency	currency_symbol	euro_value
EUR	€	1
USD	$	0.84

Answer 1

试试这样的东西：

SELECT
worker_id
,sum(case when payment_status = “1” 
      then paid_price else 0 end) as Total_paid
,sum(case when payment_status = “0” and chosen = true
      then paid_price else 0 end) as Total_outstanding
,sum(case when (payment_status = “1”) 
     or (payment_status = “0” and chosen = true)
      then paid_price else 0 end) as Total_pledged
from community_grants
group by worker_id

Answer 2

考虑使用 Postgres 的 FILTER 子句进行条件聚合，在该子句中将数据转换为计算出的条件列。

下面假设值之和是计算价格的总和，表示为：region_reference.base_price * currency_exchange.euro_value。根据需要进行调整。

SELECT h.worker_id
   , SUM(r.base_price * ce.euro_value) FILTER(WHERE
        cg.payment_status = 1
     ) AS total_paid
   , SUM(r.base_price * ce.euro_value) FILTER(WHERE
        cg.payment_status = 0 AND 
        cg.chosen=True
     )  AS total_outstanding
   , SUM(r.base_price * ce.euro_value) FILTER(WHERE
        (cg.payment_status = 1) OR 
        (cg.payment_status = 0 AND cg.chosen=True)
     )  AS total_pledged

FROM  community_grants cg
INNER JOIN region_reference r
  ON  r.community_id = cg.community_id
  AND r.region_id = cg.region_id
INNER JOIN HealthWorkers h
  ON  h.worker_id = cg.worker_id
  AND h.worker_id = 'malawi_01'
INNER JOIN currency_exchange ce
  ON ce.currency = h.preferred_currency

GROUP BY h.worker_id

使用每列的选择性聚合从两列创建 SQL 值

Creating SQL values from two columns using the selective aggregate of each column

sql

postgresql

aggregate-functions