How to combine multiple mirrors

I have three boards in my workspace. The first board shows all of my contacts and contains a column named “Event History”. My other two boards are for events we’ve hosted, and the boards contains the contacts that attended each event. How do I add a column to my “All Contacts” board that reflects if/when a contact attended one or both of my events? The email address field on all three boards can be used as the link/unique ID. I’d like the “All Contacts” board to update automatically when I add new boards for additional events. Is this possible?

Thanks for any ideas or assistance.

On your events board - what kind of column are you using to show which attendees went? Ie a connected column?

Desiree