title: RethinkDB filter and retrieve value from nested array
body: <p>Using the following query:</p>
  
  <pre><code>r.db('somedb').table('sometable')('users')
  </code></pre>
  
  <p>I get the following data from the result:</p>
  
  <pre><code>[
     [
        {
           "fn": "dpw",
           "u": "usertwo"
        },
        {
           "fn": "dwd",
           "u": "userone"
        }
     ]
  ]
  </code></pre>
  
  <p>I would like to <strong>take the field "u"</strong> and <strong>specify lets say "usertwo"</strong> and <strong>get the value of "fn"</strong> for that "u". I want to have the result <strong>filtered using ReQL</strong> so that I am not just parsing the json result in nodejs as the result will be enormous eventually. What would be the best and <strong>most efficient</strong> approach. I am new to RethinkDB and would appreciate if you could <strong>explain</strong> the answer as best you can.</p>