title: select whitout empty rows in postgresql
body: <p>I have a fun issue in postgresql.</p>
  
  <pre><code>select sum(value1) as v1,
     sum(value2) as v2,
     sum(value3) as v3,
     sum(value4) as v4,
     sum(value5) as v5,
     ...
  from (select * from test limit 0)x;
  </code></pre>
  
  <p>result:</p>
  
  <pre class="lang-none prettyprint-override"><code>  v1 |  v2 |  v3 |  v4 |  v5 |  ...
  -----+-----+-----+-----+-----+--...
       |     |     |     |     |  ...
  (1 row)
  </code></pre>
  
  <p>Expected: (0 row).</p>
  
  <p>Truth:    (1 row).</p>
  
  <p>I don't want to get empty rows.
  How can I get correct results for this case.
  Thanks.</p>