SUM two CASE functions

Question

I am trying to SUM two CASE functions that I just created in my query. I need both of these columns to return in my result set, but also need the sum of the two columns to return in another column as 'DegreeDays.' I tried the SUM function, but to no avail, and I tried a simple a 'HeatingDegreeDays + CoolingDegreeDays AS DegreeDays' and that didn't work either. Suggestions?

  ,CASE
    WHEN TempLow > 60.5                     THEN 0
    WHEN ((TempHigh + TempLow)/2) > 60.5    THEN ((60.5-TempLow)/4)
    WHEN  TempHigh >= 60.5                  THEN (((60.5 - TempLow)/2)-((TempHigh-TempLow)/4))
    WHEN TempHigh < 60.5                    THEN (60.5-(TempHigh+TempLow)/4)
   END AS HeatingDegreeDays

  ,CASE
    WHEN TempHigh < 66.25                   THEN 0
    WHEN ((TempHigh + TempLow)/2) < 66.25   THEN ((TempHigh-66.25)/4)
    WHEN  TempLow <= 66.25                  THEN (((TempHigh - 66.25)/2)-((66.25-TempLow)/4))
    WHEN TempLow > 66.25                    THEN ((TempHigh+TempLow)/2)-66.25
   END AS CoolingDegreeDays

Answer 1

You can repeat the formulas:

  ,CASE
    WHEN TempLow > 60.5                     THEN 0
    WHEN ((TempHigh + TempLow)/2) > 60.5    THEN ((60.5-TempLow)/4)
    WHEN  TempHigh >= 60.5                  THEN (((60.5 - TempLow)/2)-((TempHigh-TempLow)/4))
    WHEN TempHigh < 60.5                    THEN (60.5-(TempHigh+TempLow)/4)
   END +
   CASE
    WHEN TempHigh < 66.25                   THEN 0
    WHEN ((TempHigh + TempLow)/2) < 66.25   THEN ((TempHigh-66.25)/4)
    WHEN  TempLow <= 66.25                  THEN (((TempHigh - 66.25)/2)-((66.25-TempLow)/4))
    WHEN TempLow > 66.25                    THEN ((TempHigh+TempLow)/2)-66.25
   END AS TotalDays

Or you can put it in a subquery (or CTE) and say:

select . . .,
       (HeadingDegreeDays + CoolingDegreeDays) as TotalDays