title: How to find Sum of positive values and negative values separately in a column
body: <p>If there is a column number which has 5 rows as follows:</p>
  
  <pre><code>+----------+
  |  values  |
  +----------+
  |   -2     |
  |   -1     |
  |    0     |
  |    1     |
  |    2     |
  |    3     |
  +----------+
  </code></pre>
  
  <p>I need the sum of all negative values and the sum of all positive values in my resultset.</p>