title: Puzzling superset in SQL
body: <p>I'm querying a database (SQL) to find systems sending requests to see which are various different versions of windows (and other OSs). I check for a few known flavours and then try to get a catch-all but the catch-all catches fewer than the individual terms and I can't work out why.</p>
  
  <p>e.g. for this PHP/SQL:</p>
  
  <pre><code>$monthSelect = "SELECT DISTINCT(host) FROM $table WHERE date &gt; ('$lastMonth') ";
  $v61 = $db-&gt;query($monthSelect."AND sys LIKE '%win32_v6.1%'")-&gt;num_rows;
  echo "v61: $v61&lt;br&gt;\n";
  $v62 = $db-&gt;query($monthSelect."AND sys LIKE '%win32_v6.2%'")-&gt;num_rows;
  echo "v62: $v62&lt;br&gt;\n";
  $nWin = $db-&gt;query($monthSelect."AND sys LIKE '%win32_v%'")-&gt;num_rows;
  echo "nWin: $nWin&lt;br&gt;\n";
  </code></pre>
  
  <p>I get the following output:</p>
  
  <pre><code>v61: 1907
  v62: 2181
  nWin: 4036
  </code></pre>
  
  <p>Where 4036 is obviously less than 2181+1907. But shouldn't <code>$nWin</code> be providing a superset of the <code>$v62</code>, <code>$v61</code> and any other versions that are being found?</p>
  
  <p>I'm at a loss as to how I could be getting these answers</p>