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:
This variable is available for record/row creation and updating, and contains the state of a row after a proposed change, allowing you to selectively allow or deny certain changes. See checking new values for details.
Now if we try to add a new row with an existing code, we get a helpful error: