Calculation of the cost of goods sold

Question

I have two tables: one for incoming inventory and one for outgoing resources, which look something like this:

               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
--------------+----------+-------+-----------

I would like to have a view that looks like this:

                             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
--------------+----------+-------------+------------+-----------+-----------+----------

I can handle the overall price and average cost of goods sold, but FIFO and LIFO requests kick me where it hurts.

Is this reasonable or even possible? Any help would be greatly appreciated.

Answer 1

, FIFO . : 1. " " 2. "COGS" 3. , COGS ( ) . , .