Make changes to a database based on object names

Hi! I am stuck on a problem I would really like help with.
Suppose I have DB1:
Potatoes 5
Milk 6
Eggs 10

and DB2:

Potatoes 1
Milk 2

I want to be able to subtract the inventory numbers of DB2 from that of DB1, based on the object name. I suspect the answer lies somewhere in using schedule API workflow on a list, so I purchased the personal plan. But I still have no idea how to do this.Any help is appreciated.

Also I saw that scheduled workflow will run monthly on this plan, is this something I should worry about? Because this action needs to be done daily, like all the time.

Thanks again.

You are using third party databases?

no, we are creating the databases from other pages. You can treat the first one as a shop inventory, the second one as customer’s order.

I believe you are doing something simple in very hard way, tell us or show the editor what exactly you want to do.

I am trying to set up a simple e-commerce platform. there is an inventory database with name, quantity and price. The customer chooses an item, specifies the quantity, presses a “Save button” and that creates a Product datatype and displays his orders in a repeating group. After completing his order, he then clicks on a confirm button. The Product objects are then added as a list to the current User, and the inventory is deducted accordingly.