I'm working with a site that has a few thousand user accounts. With the exception of core accounts with CP access, each user account exists for the purpose of access to event URLs which eventually expire.
But, although the vast majority of users belong to only one event-specific user group, a select few belong to more than one.
For the purposes of housekeeping, I'd like to be able to easily find such user accounts, so I can exclude them from a periodic account deletion process.
What query could serve this purpose for a report of multi-user-group users?