title: summing all values in each row
body: <p>I have a table like:</p>
  
  <pre><code>col1 col2 col3 total
  3    5    6
  7    8    null
  ...
  </code></pre>
  
  <p>I want the total column to the sum of col1, col2, col3 for each for. So in the case, total should be:</p>
  
  <pre><code>col1 col2 col3 total
  3    5    6    14
  7    8    null 15
  ...
  </code></pre>
  
  <p>What is the quickest to up the entire total column for this?</p>