title: SQL sum result of count
body: <p>I want to sum results of count function.</p>
  
  <p>Count result looks like:</p>
  
  <pre><code>1. 16
  2. 32
  3. 0
  4. 12
  </code></pre>
  
  <p>and I want to sum it.</p>
  
  <p>I tried </p>
  
  <pre><code>select sum(count(...)) ...
  </code></pre>
  
  <p>It is not working. Also the following:</p>
  
  <pre><code>select sum(du) from (select ... as du ..)
  </code></pre>
  
  <p>Not working either.</p>