I am building an inventory system using Django, right now I am adding the functionality to place an order. What I want to do is to subtract the quantity ordered from the quantity in the database. For example if someone ordered 10boxes of chips and I have 11 in my stock once I place the order on web I want the web to subtract 10 boxes from the stock. I am not really sure how to do that. Any help is appreciated!
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You do: `11 - 10 = 1`. Is that what you're asking? Else you need to be more elaborate. Where exactly you are facing the problem. – Rohit Jain Jul 22 '20 at 07:34
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No of course am not asking for that, what I mean is that i might enter any value other than 10 and whatever value I enter should be subtracted from the value in the database. – AliReda-M Jul 22 '20 at 07:39
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Try searching for `F` function in Django ORM. That should solve your issue. Well, had you gone through the document, you would have found it. – Rohit Jain Jul 22 '20 at 07:41
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Assuming that the model name is Inventory, item_code is the identification code of the ordered item, and ordered_amount is the amount ordered from your web interface. I would do the following:
(1) retrieve the item from inventory
item = Inventary.objects.get(id=item_code)
(2) update amount
item.amount = item.amount - ordered_amount
(3) save new value for item
item.save()
You can find a similar question here.
Williams Rizzi
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It depends how you access the inventory, and you implement the save, as you can see here https://stackoverflow.com/questions/1645269/concurrency-control-in-django-model – Williams Rizzi Jul 22 '20 at 07:54