Welcome to the community, @Pierre_Boccon-Gibod!
Formulas can’t check for duplicate records, because formulas can only see their own row or linked rows.
Welcome to the Airtable community!
It is technically possible to detect duplicates with a combination of formulas/rollups. I wrote about it in this thread. At the time I wrote the solution, it required a single manual step (linking the record to the “control”), and that step can now be automated with the new Automations feature. However, this method isn’t practical in real life. It doesn’t scale and it is very resource intensive, and it only flags duplicates.
There are other better methods of detecting duplicates, as ScottWorld mentioned.
A closer look at your workflows, base design, and your subscription level (free, plus, pro) would help to determine what method to take.
Are you entering new products one at a time rather infrequently? If so, adding a step to search for the product first might be the easiest solution.
Are you doing a bulk import via copy/paste where the product codes can appear multiple times in multiple rows, and you just want to know about the new codes? Maybe you should move the product codes to a linked table with the product code as the primary field in the linked table. When you do the paste, the Airtable will create a new row in the linked table only if it doesn’t exist yet.
There are many other possible scenarios, each with a different solution.
Thank you for your response.
I currently have a pro subscription to Airtable.
I enter new products several times a month, so I was hoping to be able to automate the search for duplicates.
When I enter a new product in my database I fill in a form, so I don’t see which codes are already applied to the others…
I have to go back to the data table and create a dashboard…
It seems long and requires a lot of steps…