Access Rules to Restrict Duplicate Records#

Suppose we have a table listing airports, and we want to forbid entry of a new record with the same airport code as an existing one. In the table, we can add a column named Count that counts how many records have the same code as each other:

To understand this formula, visit our formula cheat sheet example for finding duplicates.

Now, we can add an access rule to forbid any record update or creation that would result in a Count above one. We can also include a memo to explain the problem:

Now if we try to add a new row with an existing code, we get a helpful error:

See Access rule conditions for details on writing access rule conditions, and Formulas to learn more about using formulas in columns.