How do you let users only add one row?

[EnderCodesLol]

I am making an app for my friend who is conducting a poll. He wants everyone to only add one vote. How can I let users only add one row to the app, then no more?

[Suvrutt_Gurjar]

Please take a look at the valid_if expression for avoiding duplicates in the last section of the article below.

You could use that valid if on the email column of the user.

https://help.appsheet.com/en/articles/961274-list-expressions

[EnderCodesLol]

I would more like to only show the action to add a new entry only if the useremail is not in my data set. Is there a way to do that?w

[Marc_Dillon]

Search for "prevent duplicates"

[Steve]

Use the Only if this condition is true setting or the table's Add action.