title: SQL: sum 3 columns when one column has a null value?
body: <pre><code>SELECT 
      sum(TotalHoursM)
            + (TotalHoursT)
            + (TotalHoursW)
            + (TotalHoursTH)
            + (TotalHoursF) 
            AS TOTAL
  FROM LeaveRequest
  </code></pre>