This query only needs to be run prior to requesting an upgrade to 2020.3 or newer. It will allow your Organization to locate multiple Equipment that shares a MAC Address. In 2020.3, a constraint is placed on MAC Address fields being unique across the system.
Duplicate MAC Address Locator for Oracle and MySQL
Service Desk Cabling
SELECT * FROM EQUIPMENT WHERE MAC_ADDRESS IN (SELECT MAC_ADDRESS FROM EQUIPMENT E2 GROUP BY E2.MAC_ADDRESS HAVING COUNT(E2.MAC_ADDRESS) > 1)