@user36079
The below query gives the number of distinct profiles that entered the given journey in the given time frame.
SELECT count(distinct _experience.journeyOrchestration.stepEvents.profileID)
FROM journey_step_events WHERE _experience.journeyOrchestration.stepEvents.journeyVersionID = '<journeyVersionID>'
AND _experience.journeyOrchestration.stepEvents.nodeType='start'
AND _experience.journeyOrchestration.stepEvents.instanceType = 'unitary'
AND DATE(timestamp) > (now() - interval '<last x hours>' hour);