title: Union merging different columns
body: <p>I have two tables:</p>
  
  <p><code>Table1</code>:</p>
  
  <pre><code>DATAID|   NAME   | FACTOR
  
   1    |   Ann    |   1
   2    |   Kate   |   1
   3    |   Piter  |   1 
  </code></pre>
  
  <p><code>Table2</code>:</p>
  
  <pre><code>DATAID|   NAME   | FACTOR
  
   1    |   John    |   2
   6    |   Arse    |   2
   3    |   Garry   |   2 
  </code></pre>
  
  <p>I would like <code>UNION</code> those tables and get this result:</p>
  
  <pre><code>DATAID|   NAME    | FACTOR
  
   1    |   Ann     |   1,2
   2    |   Kate    |   1
   3    |   Piter   |   1,2
   6    |   Arse    |   2 
  </code></pre>
  
  <p>So when there's 2 rows with same dataid, I would like to get 'NAME' column from Table1 and some kind of aggregated FACTOR, for example '1,2' or 3</p>