从一系列带有日期的发票，我怎么可能按发票当月和之前一个月发票它们聚集？

Question

我有每行不同客户的发票的表。我想通过使用SQL（或SQL HANA）总量不仅所有同月和客户的发票，而且在另一列总从上个月去获得。

让：

Customer, Invoice Date(YearMonth), Amount
1, 201812, 12
1, 201811, 10
1, 201811, 15
1, 201811, 20
1, 201808, 12
1, 201807, 66
1, 201804, 12
1, 201801, 12    
2, ...
...

=>

Customer, YearMonth Invoices, Total Month, Total Previous Month(YM -1 )
1, 201812, 12, 45
1, 201811, 45, 0 
1, 201808, 12, 66 
1, 201807, 66, 0
1, 201804, 12, 0
1, 201801, 12, 0
2, ..

注：我也有确切的发票日期，而不是只有YearMonth

Answer 1

当上HANA数据库执行以下SQLScript提供了所需的溶液

它包含一个子查询语句，并使用诸如SUM窗口函数与PARTITION BY子句

此外，我使用日期字符串和string to date conversion functions和add_months function

select distinct
    Customer,
    InvoiceDate,
    SUM(Amount) OVER (PARTITION BY Customer, InvoiceDate) as TotalCurrent,
    (
        select sum(i.Amount) 
        from Invoices i
        where i.Customer = j.Customer and i.InvoiceDate = TO_CHAR( add_months(TO_DATE(concat(j.InvoiceDate,'01')), -1) ,'YYYYMM')
    ) as PrevTotal
from Invoices j