title: New column referencing second table - do I need a join?
body: <p>I have two tables (first two shown) and need to make a third from the first two - do I need to do a join or can you reference a table without joining?</p>
  
  <p>The third table shown is the desired output.  Thanks for any help!   </p>
  
  <pre><code>| ACC | CALL DATE |  |  |
  +-----+-----------+--+--+
  | 1 1 | 2/1/18    |  |  |
  +-----+-----------+--
  
  +-----+---------------+--+--+
  | ACC | PURCHASE DATE |  |  |
  +-----+---------------+--+--+
  | 1 1 | 1/1/18        |  |  |
  +-----+---------------+--+--+
  
  +-----+-----------+----------------------+--+
  | ACC | CALL DATE | PRIOR MONTH PURCHASE |  |
  +-----+-----------+----------------------+--+
  | 1 1 | 2/1/18    | YES                  |  |
  +-----+-----------+----------------------+--+
  </code></pre>