SELECT U.UserId, U.FirstName, EU.EventId, E.EventName, 'Yes' as RSVP, EU.Attended,

COUNT(EU.UserId) OVER (PARTITION BY U.UserId ) AS UserTotalRSVPs,

SUM(EU.Attended) OVER (PARTITION BY U.UserId ) AS UserTotalAttended

FROM EventUser EU

INNER JOIN Users U ON...