按天分组数据

Question

我有一个表transaction，数据如下：

date       | status  | delivered | products
-------------------------------------------
03.10.2014 | SUCCESS |      TRUE | 4
03.10.2014 | FAILURE |      FAIL | 0
03.10.2014 | SUCCESS |      FAIL | 1
03.10.2014 | SUCCESS |      FAIL | 4
04.10.2014 | SUCCESS |      TRUE | 24
04.10.2014 | SUCCESS |      TRUE | 5
04.10.2014 | FAILURE |      FAIL | 0

现在我想按天对数据进行分组，它看起来像：

date       | success_status | failure_status | delivered | total_products
-------------------------------------------------------------------------
03.10.2014 | 3              | 1              | 1         | 9
04.10.2014 | 2              | 1              | 2         | 29

我知道如何将(products) 求和为 total_products、按日期分组。

但是我怎样才能在查询中获得剩余的列 success_status、failure_status 和 delivered？

Answer 1

你需要做一个条件求和：

select date, 
       sum(case when status = 'SUCCESS' and delivered then products end) as success_status,
       sum(case when status = 'FAILURE' then products end) as failure_status,
       sum(case when delivered then products end) as delivered,
       sum(products) as total_products
from the_table
group by date

在即将到来的 9.4 版本中，您将能够更优雅地编写此代码（并且可能更清楚地了解 case 正在做什么）

SELECT date, 
       sum(products) filter (status = 'SUCCESS' and delivered) as large_orders_amount,
       sum(products) filter (status = 'FAILURE') as failure_status,
       sum(products) filter (delivered) as delivered,
       sum(products) as total_products
from the_table
group by date

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顺便说一句：date 是一个可怕的列名称。一方面因为它也是一个保留字，但更重要的是它没有记录该列包含的内容。交货日期，接收日期，取消日期，...？