Joining Collections in Firebase

This might be a newbie question so please excuse my ignorance.

I have two collections in Firebase, Users, and Actions. Within those collections:

  • Users contain a unique identifier UserID.
  • Actions also contain a unique identifier UserID.

I am attempting to join these two collections in Make to send an email out as the email needs information from both collections. I can read the database but am unable to make a join showing actions just related to a user.

Should I join the two tables into an intermediate table that reads or can I do all of this in and if so, how would I do that?