title: sqlite3 select from empty table = no select?
body: <p>I usq sqlite3 (on Android) and try to return a default value, if a select has to handle <code>NULL</code> values.</p>
  
  <p>Normally this works:</p>
  
  <pre><code>SELECT ifnull(NULL, 12);
  12
  </code></pre>
  
  <p>With a variable:
      SELECT ifnull(var, 21) from (select NULL as var);
      21</p>
  
  <p>But the moment I use a table and this table is empty, then I don't get anything:</p>
  
  <pre><code>SELECT ifnull(_id, 1) FROM empty_table;
  &lt;nothing here&gt;
  </code></pre>
  
  <p>Even returning a simple number is not possible:</p>
  
  <pre><code>SELECT 123;
  123
  SELECT 234 FROM empty_table;
  &lt;nothing here&gt;
  </code></pre>
  
  <p>Why does that happen? How can I still get a value out of it?</p>