Question

在一个相当简单的数据库（Firebird 3.0）中，我有一个库存表，其中包含与产品相关的字段：

购买

QTY     PRICE   VALUE    Date
10      10      100      1.12.2018
25      9       225      5.12.2018
30      8       240      12.12.2018
50      7       350      14.12.2018
100     6       600      22.12.2018

总计（数量，价格，价值）：215、40、1515

在这里，已售数量为150，我需要对“购买”中最早的记录求和（值），直到sum(QTY) = SOLD QTY。

Answer 1

使用Firebird 3支持的 Windowed Aggregates 可以轻松解决此问题。

select *
  ,case when cumulative_qty <= sold_qty then qty
        when sold_qty-(cumulative_qty - qty) < 0 then 0
        else sold_qty-(cumulative_qty - qty)
   end as qty_sold
  ,case when cumulative_qty <= sold_qty then qty
        when sold_qty-(cumulative_qty - qty) < 0 then 0
        else sold_qty-(cumulative_qty - qty)
   end * price as value_sold
from
 (
   select *
     ,150 as sold_qty
      -- cumulative sum of quantity in stock (FIFO)
     ,sum(qty) over (order by date rows unbounded preceding) as cumulative_qty
   from tab
 ) as dt
;

现在您可以计算总和：

select 
  sum(case when cumulative_qty <= sold_qty then qty
           when sold_qty-(cumulative_qty - qty) < 0 then 0
           else sold_qty-(cumulative_qty - qty)
      end) as qty_sold
  ,sum(case when cumulative_qty <= sold_qty then qty
            when sold_qty-(cumulative_qty - qty) < 0 then 0
            else sold_qty-(cumulative_qty - qty)
       end * price) as value_sold
from
 (
   select *
     ,150 as sold_qty
      -- cumulative sum of quantity in stock (FIFO)
     ,sum(qty) over (order by date rows unbounded preceding) as cumulative_qty
   from tab
 ) as dt
;

请参见db<>fiddle（使用Postgres，但Firebird语法应相同）

FIFO逻辑的实现

1 个答案: