title: How to get a list of a values from a single ActiveRecord column?
body: <p>Code like this</p>
  
  <pre><code>my_id_results = MyTable.select("some_id").as_json
  </code></pre>
  
  <p>returns an array of hashes, each one of which contains both <code>id</code> and <code>some_</code></p>
  
  <pre><code>[
      {id =&gt; nil, some_id =&gt; 1},
      {id =&gt; nil, some_id =&gt; 2},
      {id =&gt; nil, some_id =&gt; 3}
  ]
  </code></pre>
  
  <p>I can map this array to a list of ids like this</p>
  
  <pre><code>my_ids = []
  my_id_results.each do |my_id_result|
    my_ids.push my_id_result['some_id']
  end
  </code></pre>
  
  <p>For cases like this, where I'm looking for a list of values for a single column, is there a way to return the flat array directly from ActiveRecord?</p>