Query % of x item based on x+y total - sql

Question

I'm running a SQL command which returns me the following table
What I need now, is to retrieve how much % corretiva is from total, and how much % preventiva is from total for each month, so there must be another 2 columns like preventivas% and corretivas% as example, I know MES.1 (month 1), will return preventiva =100%, and corretiva = 0%,
This is my query
SELECT
MONTH(workOrderDate) AS MES,
(SUM(CASE WHEN WorkType = '02' AND workOrderDescription = 'preventiva' THEN 1.0 ELSE 0 END)) AS preventiva,
(SUM(CASE WHEN workOrderDescription = 'CORRETIVA' THEN 1 ELSE 0 END)) AS corretivas,
SUM(CASE WHEN WorkType = '02' AND workOrderDescription = 'preventiva' THEN 1.0 ELSE 0 END + CASE WHEN workOrderDescription = 'CORRETIVA' THEN 1 ELSE 0 END) AS total
FROM
WorkOrder
WHERE
YEAR(workOrderDate) = 2018
AND lastUpdateData IS NOT NULL
GROUP BY
MONTH(workOrderDate);
I can't seem to figure out how to achieve the wanted result, would anyone please help me?
Thanks!

Answer 1

You can take your existing query, put it into a CTE, and then calculate your percentages in the main SELECT, like this:
;WITH subresults AS
(
SELECT
MES = MONTH(workOrderDate)
,preventiva = ( SUM(CASE WHEN WorkType = '02'
AND workOrderDescription = 'preventiva'
THEN 1.0
ELSE 0 END
)
)
,corretivas = ( SUM(CASE WHEN workOrderDescription = 'CORRETIVA' THEN 1 ELSE 0 END))
,total = SUM(CASE WHEN WorkType = '02'
AND workOrderDescription = 'preventiva'
THEN 1.0
ELSE 0 END + CASE WHEN workOrderDescription = 'CORRETIVA' THEN 1 ELSE 0 END
)
FROM WorkOrder
WHERE
YEAR(workOrderDate) = 2018
AND lastUpdateData IS NOT NULL
GROUP BY MONTH(workOrderDate)
)
SELECT
s.MES
,s.preventiva
,s.corretivas
,s.total
,preventivasPct = CASE WHEN s.total <> 0 THEN (s.preventiva / s.total) * 100.0 ELSE NULL END
,corretivasPct = CASE WHEN s.total <> 0 THEN (s.corretivas / s.total) * 100.0 ELSE NULL END
FROM subresults s
EDIT: I added CASE statements to preventivasPct and corretivasPct. When the total is 0, the CASE will return NULL. Feel free to change NULL to some other value if you want. I've found that usually 0 or NULL is the correct answer when encountered with divide-by-zero when calculating percentages.