Help with detecting duplicates in a field

[Janene_Pappas]

I’ve attempted to follow the recommendations here to detect duplicates in a field but have not been successful and could use some expert eyes on what I’ve implemented. I did put a reply on that thread but since it’s a couple of years old, figured I should start my own question. Here are 2 screenshots from the 2 tables in play. Anyone see where I went wrong? TIA!

[Kamille_Parks · Accepted solution]

values is a pure array, the formula you wrote needs to handle strings. So replace all instances of values with ARRAYJOIN(values)

[Janene_Pappas]

Thanks for the reply @Kamille_Parks

I thought the field {All IDs} being an ARRAYJOIN already would then be put into the Number of IDs rollup as the long text result of the ARRAYJOIN?

[Kamille_Parks]

You’re doing a rollup of a rollup. So you’re still dealing with an array of strings, even though every record is linked to just one record its still an array.

[Janene_Pappas]

Thank you for the explanation and this worked great!

[Tito_Alverio]

I needed a similar setup and this worked for me. Having a rollup detect when an email is used multiple times as a way to track a duplicate person entry.