SQL to check if user has RSVP'd to an event

My users remain confused about how to get access to post on an event timeline. It's not clear that they need to RSVP first... I'm trying to write some code in the event page module position which will alert them to RSVP in order to post...

I need some help working out which EasySocial table(s) to query to help with this. I'm trying to see if the current logged in user has RSVP'd to the event being viewed... I guess it's something like

SELECT from some EasySocial table(s) WHERE UserID = CurrentLoggedin

I'm able to do the PHP bits that would get the current UserID and evaluate the result of this select to show a message if needed.. but it's just which table(s) to look at is what I'd need... and maybe there would be some PHP first as well to extract the current event ID.

Thanks for any help!