Postgres FIFO查询计算利润率

Question

我正在处理我的库存系统查询，以在 PostgreSQL (9.3+) 中根据 FIFO（先进先出）计算利润。大多数回复都是针对 MS SQL 服务器的，所以我不确定如何针对 PostgreSQL 进行处理。我曾尝试使用 Windows 函数，但在计算利润时遇到困难（我不确定我们 need/can 是否使用游标，因为我以前没有使用过它们）

销售额（负数量）约为 (20*4 + 30*1) = 110
基于 FIFO 的商品销售成本为 (5*2 + 10*2 + 10*1) = 40
利润应该是 110 - 40 = 70

到目前为止，我已经设法计算出运行总数。有人可以帮忙吗？

http://sqlfiddle.com/#!15/50b12/6

product_id product_name product_price purchase_date        product_quantity
1          Notebook     5             2017-05-05 00:00:00  2
1          Notebook     10            2017-05-06 00:00:00  4
1          Notebook     15            2017-05-07 00:00:00  6
1          Notebook     20            2017-05-08 00:00:00  -4 (this is sale)
1          Notebook     30            2017-05-09 00:00:00  -1 (this is sale)

所需结果应显示销售额和利润率。只要我能得到利润率，它就会解决我的问题。

Answer 1

select *,
    sum(price_sold - price_purchased) over(order by rn) as profit 
from
    (
        select 
            row_number() over(order by purchase_date, product_id) as rn,
            product_id, product_price as price_purchased
        from inv_test, generate_series(1, abs(product_quantity))
        where product_quantity > 0
    ) p
    full join
    (
        select
            row_number() over(order by purchase_date, product_id) as rn,
            product_id, product_price as price_sold
        from inv_test, generate_series(1, abs(product_quantity))
        where product_quantity < 0
    ) s using (rn, product_id)
;
 rn | product_id | price_purchased | price_sold | profit 
----+------------+-----------------+------------+--------
  1 |          1 |               5 |         20 |     15
  2 |          1 |               5 |         20 |     30
  3 |          1 |              10 |         20 |     40
  4 |          1 |              10 |         20 |     50
  5 |          1 |              10 |         30 |     70
  6 |          1 |              10 |            |     70
  7 |          1 |              15 |            |     70
  8 |          1 |              15 |            |     70
  9 |          1 |              15 |            |     70
 10 |          1 |              15 |            |     70
 11 |          1 |              15 |            |     70
 12 |          1 |              15 |            |     70

Postgres FIFO查询计算利润率

Postgres FIFO query calculate profit margin

sql

postgresql

cursor