[LeetCode] Reformat Department Table (sum, case, when, then)

SELECT id 
	 , SUM(CASE WHEN month = "Jan" THEN revenue END) AS Jan_Revenue
         , SUM(CASE WHEN month = "Feb" THEN revenue END) AS Feb_Revenue
         , SUM(CASE WHEN month = "Mar" THEN revenue END) AS Mar_Revenue
         , SUM(CASE WHEN month = "Apr" THEN revenue END) AS Apr_Revenue
         , SUM(CASE WHEN month = "May" THEN revenue END) AS May_Revenue
         , SUM(CASE WHEN month = "Jun" THEN revenue END) AS Jun_Revenue
         , SUM(CASE WHEN month = "Jul" THEN revenue END) AS Jul_Revenue
         , SUM(CASE WHEN month = "Aug" THEN revenue END) AS Aug_Revenue
         , SUM(CASE WHEN month = "Sep" THEN revenue END) AS Sep_Revenue
         , SUM(CASE WHEN month = "Oct" THEN revenue END) AS Oct_Revenue
         , SUM(CASE WHEN month = "Nov" THEN revenue END) AS Nov_Revenue
         , SUM(CASE WHEN month = "Dec" THEN revenue END) AS Dec_Revenue

FROM department
GROUP BY id

SUM() function calculates the sum of a set of values.

Note: NULL values are ignored.