Hi Bernardo ,
To understand that an object repeats twice, you must first select an attribute as a key within that entity. For your example I want to explain here, each object in the product entity can have an EAN number. When we think that this will be unique, we can detect that it has been registered via this number before.
Let's also assume that we are importing this information using excel importer . It also allows you to specify a data type as a key of the items in the list to be imported when using the Excel importer module. Thus , it prevents you from saving an item to the database twice .
My suggestion for you to do this in microflow is:
Retrieve all the products from the database. Iterate the products you want to add database to in a loop. In the loop , detect products with conflicting Ean numbers by using the list filter .
I hope this helps for you ,