Can anyone help me with this algorithm?(FIFO based inventory)

Hi all..I'm a little bit confuse with this problem.
I have 3 tables, stock_in, stock_level, and stock_out.
stock_in used for save the data product when there's new purchase.
stock_out used for save the data product out.
stock_level used for count how many stock in warehouse.

When user input the product data, automatically its enter to stock_level. And, when there's stock out, automatically decrease the stock_in_unit on stock_level table with FIFO base.

for example (the column is just, date, stock_in_unit to make easy)
Product purchased (saved to stock_in and stock_level)
Product Out
Because I use FIFO, so, on stock_level table now fill with
I have do until this step, but the problem is :
How about if, for example, the user make a mistake, the product out should be 3, and not 7, how can I do the edit?because, the stock_level table now should be
I'm confuse how the algorithm to do that. Please give any suggestions. All appreciated.

Thank you so much

re: Can anyone help me with this algorithm?(FIFO based inventory)

can anyone help please?
I'm still stuck to think this problem :(

re: Can anyone help me with this algorithm?(FIFO based inventory)

Heya, doxtor.

In this case, you'd want the User to be able to manually alter the values. What database software are you using?

re: Can anyone help me with this algorithm?(FIFO based inventory)

Hi..
Sorry for late in answering. I use mysql database. For language I use php 5.

Thank you so much for replying

re: Can anyone help me with this algorithm?(FIFO based inventory)

The easiest solution would be to allow the User to add an adjustment (you could add this as a row to the `stock_in` or `stock_out` table with an additional flag [column] that denotes that it is an adjustment).

The other option would be to allow the User to directly edit the `stock_in` and/or `stock_out` tables (set up an interface similarly to how phpMyAdmin does it, for example), and the rebuild the `stock_level` table since that date.

E.g., if the User edits `stock_in` on 2008-06-01, then you would need to run through and recalculate the `stock_level` values where `in_date` >= '2008-06-01'.

This might get somewhat complicated because you have a `stock_in` and a `stock_out` table; you might want to consider combining them into a single `stock_activity` table; simply add an additional column that you can use to specify the type of the change (shipment, sale, adjustment, return, etc.).

re: Can anyone help me with this algorithm?(FIFO based inventory)

Yes, this become complicated, because i have 3 tables to stock activity. Do you have any suggestion, e.g, how can i use just 1 table for stock in and out, and the adjustment?

For stock in adjustment, it's more easy than stock out adjustment. Like you said, just recalculate stock_level where date ....
The biggest problem is on 'stock_out' adjustment. Am I make mistake with 3 tables?

Can you explain this option to combine with stock_out adjustment? I think the idea to rebuild the stock_level is good, but, how can adjust the stock_out activity?
sorry if I'm asking to much, because I'm confuse :(
thank you so much