title: rethinkdb eqJoin matching
body: <p>Hi I'm using javascript with rethinkdb, and I'm trying to figure out how to use eqJoin when the id of the target is not on the maintable but on the second table.</p>
  
  <p>The examples on the website shows this.</p>
  
  <pre><code>first table /players
  [{name: 'anna', gameID:1}]
  
  second table /games
  [{id: 1, gameName: 'supergame'}]
  </code></pre>
  
  <p>But what I want to join is this</p>
  
  <pre><code>first table / players
  [{id 1, name: 'anna'}]
  
  second table / games
  [{playerID: 1, gameName:'supergame'},
   {playerID: 1, gameName:'megagame'},
   {playerID: 1, gameName:'lamegame'}]
  </code></pre>
  
  <p>I have read a little about concatMap and tried this but that obviously gives me errors, is there any other way?</p>
  
  <p>And if there is could I even join even more tables?</p>
  
  <pre><code>r.table("players").concatMap(function(play) {
      return r.table("games").getAll(
          play("id"),
          { index:"playerID" }
      ).map(function(games) {
          return { left: play, right: games }
      })
  }).run(conn, callback)
  </code></pre>