title: Populate column nulls with next non-null value
body: <p>Is there a straightforward query to fill in the gaps in a column with the next non-null value in that column?  I want a column which has data like this:</p>
  
  <pre><code>--------------------
  | ID | Version     |
  --------------------
  |  1 | '162.39'    |
  --------------------
  |  2 | NULL        |
  --------------------
  |  3 | NULL        |
  --------------------
  |  4 | '162.40'    |
  --------------------
  |  5 | '162.41'    |
  --------------------
  |  6 | NULL        |
  --------------------
  |  7 | NULL        |
  --------------------
  |  8 | '162.42'    |
  --------------------
  |  9 | '162.42'    |
  --------------------
  | 10 | NULL        |
  --------------------
  </code></pre>
  
  <p>To end up like this</p>
  
  <pre><code>--------------------
  | ID | Version     |
  --------------------
  |  1 | '162.39'    |
  --------------------
  |  2 | '162.40'    |
  --------------------
  |  3 | '162.40'    |
  --------------------
  |  4 | '162.40'    |
  --------------------
  |  5 | '162.41'    |
  --------------------
  |  6 | '162.42'    |
  --------------------
  |  7 | '162.42'    |
  --------------------
  |  8 | '162.42'    |
  --------------------
  |  9 | '162.42'    |
  --------------------
  | 10 | NULL        |
  --------------------
  </code></pre>
  
  <p>The last value(s) can either be <code>'162.42'</code> or remain at <code>NULL</code>.</p>