Inventory database design [closed]

Answer 1

I have seen both approaches at my current company and would definitely lean towards the first (calculating totals based on stock transactions).

If you are only storing a total quantity in a field somewhere, you have no idea how you arrived at that number. There is no transactional history and you can end up with problems.

The last system I wrote tracks stock by storing each transaction as a record with a positive or negative quantity. I have found it works very well.

Answer 2

Is not having one or two columns, what I meant with "totaling inventory received - total of inventory sold" is something like this:

Select sum(quantity) as inventory_received from Inventory_entry
Select sum(quantity) as inventory_sold from Sales_items

then

Qunatity_on_hand = inventory_received - inventory_sold

Please keep in mind that I oversimplified this and my initial explanation. I know there is much more to inventory that just keeping track of quantities, but in this case that's were the problem lies and what we want to fix. At this point the reason to change it is preciselly the cost of supporting the problems caused by the current design.

Also I wanted to mention that although this is not a "coding" question is related to algoritms and design which IMHO are very important topics.

Thanks everybody for your answers so far.

Nelson Marmol

Answer 3

I would opt for the first way, where

the quantity on hand is calculated totaling inventory received - total of inventory sold

The Right Way, IMO.

EDIT: I would also want to factor in any stock losses/damages into the system, but I'm sure you have that covered.

Answer 4

Django-inventory geared more to fixed assets, but might give you some ideas.

IE: ItemTemplate (class) -> ItemsOnHand (instance)

ItemsOnHand can be linked to more ItemTemplates; Example Printer & the ink cartridges is requires. This also allows to set Reorder points for each ItemOnHand.

Each ItemsOnHand is linked to InventoryTransactions, this allows for easy auditing. To avoid calculating actual on hand items from thousand of invetory transactions, checkpoints are used which are just a balance + a date. To calculate items on hand query to find the most recent checkpoint and start adding or substracting items to find the current balance of items. Define new checkpoints periodically.

Answer 5

It depends, inventory systems are about far more than just counting items. For example, for accounting purposes, you might need to know accounting value of inventory based on FIFO (First-in-First-out) model. That can't be calculated by simple "totaling inventory received - total of inventory sold" formula. But their model might calculate this easily, because they modify accounting value as they go. I don't want to go into details because this is not programming issue but if they swear by it, maybe you didn't understand fully all their requirements they have to accommodate.

Answer 6

Take a look at the ARTS (Association for Retail Technology Standards) data model (http://nrf-arts.org). It uses a StockLedger table with a record each item and changes to the inventory are all tracked in InventoryJournalEntries.