title: Multiple platform ID assignments to email address
body: <p>Interesting issue I'm facing.  I have 5 company tables that contain user information.  What I'd like to do have is an aggregate table of all the user id's associated to an email across the 5 companies. </p>
  
  <p>i.e.  Company 1 (id, email), Company 2 (id, email), Company 3 (id, email). </p>
  
  <p>Ideally, would like the table to read (email, c1_id, c2_id, c3_id). </p>
  
  <p>Scratching my head on how to get all the distinct emails THEN company id's.</p>