This may have an embarassingly simple answer - apologies if I've missed it!
When participants come to our events, we want to know what other events they have been on, or are booked on.
I can make a Drupal View of participants and use table aggregator plus to group rows by person - enumerating that grouped row lists all the events a person has been on. But if I then filter the list by the event I'm interested in - of course we are only showing the single participation of each person on the event I filtered for. No more list of all events.
I suppose we could make a group of the event participants and filter the view based on that, but it is all seeming a rather long way round to an issue that must already have come up.
I'll be grateful for any ideas!
Civicrm 4.7.27, Drupal 7.56