title: WP_Query - multiple custom post types and sort by custom meta
body: <p>I'd like get results from two custom post types and sort them by custom meta (date of start events).</p>
  
  <p>This code:</p>
  
  <pre><code>$warsztaty_q = new WP_Query(array(
      'post_type' =&gt; array('kalendarium', 'warsztaty'),
      'order_by' =&gt; 'meta_value',
      'meta_key' =&gt; 'data_start',
      'order' =&gt; 'ASC'
  ));
  </code></pre>
  
  <p>Would be ok but first sorted is 'kalendarium' and then 'warsztaty' so in query results first sorted are posts from 'kalendarium' and next from 'warsztaty' not together.</p>
  
  <p>I found this solution:
  <a href="https://wordpress.stackexchange.com/questions/71576/combining-queries-with-different-arguments-per-post-type">https://wordpress.stackexchange.com/questions/71576/combining-queries-with-different-arguments-per-post-type</a></p>
  
  <p>But I can't get custom meta :(</p>
  
  <p>Anyone can help me? :)</p>