title: Subquery to see if a field in a separate table is null or empty for the same id
body: <p>I am getting authors this way:</p>
  
  <pre><code>$feat_authors = $wpdb-&gt;get_results("SELECT ID, user_nicename from $wpdb-&gt;users WHERE display_name &lt;&gt; 'admin' ORDER BY rand() LIMIT 3");
  </code></pre>
  
  <p>But I want to check in a seperate database table: <code>wp_usermeta</code> where there is a field <code>meta_key='description'</code> to see if its <em>value</em> <strong>is not empty or null</strong> for the associated ID (user_id and ID from the first table match).</p>
  
  <p>Selecting and printing <code>wp_usermeta</code> yields:</p>
  
  <pre><code>Array
  (
      [0] =&gt; stdClass Object
          (
              [umeta_id] =&gt; 19
              [user_id] =&gt; 2
              [meta_key] =&gt; first_name
              [meta_value] =&gt; Rita
          )
  
      [1] =&gt; stdClass Object
          (
              [umeta_id] =&gt; 20
              [user_id] =&gt; 2
              [meta_key] =&gt; last_name
              [meta_value] =&gt; Santos
          )
  
      [2] =&gt; stdClass Object
          (
              [umeta_id] =&gt; 21
              [user_id] =&gt; 2
              [meta_key] =&gt; nickname
              [meta_value] =&gt; rita
          )
  
      [3] =&gt; stdClass Object
          (
              [umeta_id] =&gt; 22
              [user_id] =&gt; 2
              [meta_key] =&gt; description
              [meta_value] =&gt; I’m the coolest person in Uniplaces. I also post stuff on Facebook and other social networks.
          )
  </code></pre>
  
  <p>And I tried this, which I know gives me all the empty descriptions: <code>SELECT * FROM wp_usermeta WHERE meta_key = 'description' AND meta_value = ''</code></p>
  
  <p>But I'm not sure how to combine them so that in the first query I only get results where the description in the second table is not empty or null. Another thing that is throwing me off is that I'm not sure how to bring the id over to the second query as the first id has a different named (ID as opposed to user_id).</p>