this query seems to result in the same as as simple "count(idvisit)" as a measure.
I think the problem is that my users trigger multiple events but I am only interested in the very last event:
event_action1 UserA 2017-11-01 14:00
event_action2 UserA 2017-11-01 15:00
event_action1 UserA 2017-11-01 15:30
event_action3 UserA 2017-11-01 16:00
The result I want is only: UserA = event_action3 at 2017-11-01 16:00