title: How can I group by on a field which has NULL values?
body: <p>I have a table with 2 fields</p>
  
  <pre><code> x          y
  ----       ----
   1         null            
   2          5
   3          5
   4         null
   5         null
   6          10
   7          5
  </code></pre>
  
  <p>And my SQLite query is</p>
  
  <pre><code>select y,count(y)
  from mytable
  group by y
  </code></pre>
  
  <p>And the result is</p>
  
  <pre><code>null    0
   5      3
   10     1
  </code></pre>
  
  <p>It is expected to see null  3.<br>
  But the output is null  0.<br>
  what does it mean?</p>