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 Adress. 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 COUNT(MAC_ADDRESS) CNT, MAC_ADDRESS FROM EQUIPMENT GROUP BY MAC_ADDRESS HAVING COUNT(MAC_ADDRESS) > 1