title: Comparing different totals between 2 tables and putting that into its own column
body: <p>The current results i have are this </p>
  
  <pre><code>| MonthYear | Table1 Amount | Table2 Amount |
  |-----------|---------------|---------------|
  |    Jun-17 |           100 |           125 |
  |    Sep-17 |            50 |            50 |
  </code></pre>
  
  <p>I am comparing the totals from the two tables on a monthly basis. When the total is different between the 2 tables i want to add the difference to another column</p>
  
  <pre><code>| MonthYear | Table1 Amount | Table2 Amount | Unknown |
  |-----------|---------------|---------------|---------|
  |    Jun-17 |           100 |           125 |      25 |
  |    Sep-17 |            50 |            50 |       0 |
  </code></pre>
  
  <p>Which i have achieved but how do i add the case statement as a row instead or a column e.g output like this</p>
  
  <pre><code>| MonthYear | Table1 Amount | Table2 Amount |
  |-----------|---------------|---------------|
  |    Jun-17 |           100 |           125 | 
  |    Sep-17 |            50 |            50 | 
  |   Unknown |               |            25 | 
  </code></pre>
  
  <p>Can this be done? Any help would be appreciated. Thanks</p>
  
  <p>SQL Fiddle - <a href="http://sqlfiddle.com/#!6/8843b/1" rel="nofollow noreferrer">http://sqlfiddle.com/#!6/8843b/1</a></p>