Sql 计算销售商品的成本

我有两个表，一个用于输入库存，另一个用于输出库存，大致如下所示：

               purchase (incoming)
--------------+----------+-------+-----------
 inventory_id | quantity | price | timestamp 
--------------+----------+-------+-----------
 bobble       |        1 | $1.00 | 2014-01-01
 trinket      |        2 | $1.00 | 2014-01-02
 trinket      |        2 | $2.00 | 2014-01-03
--------------+----------+-------+-----------


               sale (outgoing)
--------------+----------+-------+-----------
 inventory_id | quantity | price | timestamp
--------------+----------+-------+-----------
 trinket      |        1 | $3.00 | 2014-01-04
 bobble       |        1 | $3.00 | 2014-01-05
 trinket      |        2 | $3.00 | 2014-01-06
 trinket      |        1 | $3.00 | 2014-01-07
--------------+----------+-------+-----------

                             sale_with_cost_of_goods
--------------+----------+-------------+------------+-----------+-----------+----------
 inventory_id | quantity | total_price | timestamp  | cogs_fifo | cogs_lifo | cogs_avg 
--------------+----------+-------------+------------+-----------+-----------+----------
 trinket      |        1 |       $3.00 | 2014-01-04 |     $1.00 |     $2.00 |    $1.50 
 bobble       |        1 |       $3.00 | 2014-01-05 |     $1.00 |     $1.00 |    $1.00 
 trinket      |        2 |       $6.00 | 2014-01-06 |     $3.00 |     $3.00 |    $3.00
 trinket      |        1 |       $3.00 | 2014-01-07 |     $2.00 |     $1.00 |    $1.50
--------------+----------+-------------+------------+-----------+-----------+----------

我希望有一个这样的视图：

               purchase (incoming)
--------------+----------+-------+-----------
 inventory_id | quantity | price | timestamp 
--------------+----------+-------+-----------
 bobble       |        1 | $1.00 | 2014-01-01
 trinket      |        2 | $1.00 | 2014-01-02
 trinket      |        2 | $2.00 | 2014-01-03
--------------+----------+-------+-----------


               sale (outgoing)
--------------+----------+-------+-----------
 inventory_id | quantity | price | timestamp
--------------+----------+-------+-----------
 trinket      |        1 | $3.00 | 2014-01-04
 bobble       |        1 | $3.00 | 2014-01-05
 trinket      |        2 | $3.00 | 2014-01-06
 trinket      |        1 | $3.00 | 2014-01-07
--------------+----------+-------+-----------

                             sale_with_cost_of_goods
--------------+----------+-------------+------------+-----------+-----------+----------
 inventory_id | quantity | total_price | timestamp  | cogs_fifo | cogs_lifo | cogs_avg 
--------------+----------+-------------+------------+-----------+-----------+----------
 trinket      |        1 |       $3.00 | 2014-01-04 |     $1.00 |     $2.00 |    $1.50 
 bobble       |        1 |       $3.00 | 2014-01-05 |     $1.00 |     $1.00 |    $1.00 
 trinket      |        2 |       $6.00 | 2014-01-06 |     $3.00 |     $3.00 |    $3.00
 trinket      |        1 |       $3.00 | 2014-01-07 |     $2.00 |     $1.00 |    $1.50
--------------+----------+-------------+------------+-----------+-----------+----------

我可以处理销售商品的总价格和平均成本，但先进先出和后进先出的查询让我感到痛苦

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这是合理的还是可能的？任何帮助都将不胜感激。

当一位客户将存货的标准成本计算改为先进先出成本计算时，我遇到了类似的问题。我的解决办法是： 1.在采购表中添加“剩余数量”列 2.将列添加到“COGS”的销售表中 3.修改“销售订单发货”模块中的代码，以根据采购中最早的剩余数量（有时超过一行）计算COG，同时相应减少剩余数量。

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查询变得简单，因为所有数据都位于sales表中。

如何解决这一问题实际上取决于何时填充表。采购和销售是否正在更新，以便按时间顺序添加每一行？它们是否已经填充并且cogs数据在事实之后？sale和purchase表只是附加在后面，最新的在末尾。因此，如果我现在再买一个筒子，它将成为购买表的最后一行。我描述货物成本计算的方式是，它将被定义为一个视图，因此当您从中选择时，计算将在运行中进行。