SQL Pivot Columns with prefixes - sql

Question

New to SQL, struggling to fully understand the pivot clause. I have four fields (state, season, rain, snow) and am trying to pivot so that I have 5 fields (state, summer_rain, summer_snow, winter_rain, winter_snow). I'm not sure how to pivot two fields so that they are prefixed with another if that makes sense. Reprex below.
What I have now
What I'm after
My code (receiving an error when aggregating snow & rain within pivot clause):
DECLARE #myTable AS TABLE([state] VARCHAR(20), [season] VARCHAR(20), [rain] int, [snow] int)
INSERT INTO #myTable VALUES ('AL', 'summer', 1, 1)
INSERT INTO #myTable VALUES ('AK', 'summer', 3, 3)
INSERT INTO #myTable VALUES ('AZ', 'summer', 0, 1)
INSERT INTO #myTable VALUES ('AL', 'winter', 5, 4)
INSERT INTO #myTable VALUES ('AK', 'winter', 2, 2)
INSERT INTO #myTable VALUES ('AZ', 'winter', 1, 1)
INSERT INTO #myTable VALUES ('AL', 'summer', 6, 4)
INSERT INTO #myTable VALUES ('AK', 'summer', 3, 0)
INSERT INTO #myTable VALUES ('AZ', 'summer', 5, 1)
SELECT [state], [year], [month], [day]
FROM
(
SELECT * FROM #myTable
) t
PIVOT
(
sum([rain]), sum([snow]) FOR [season] IN ([summer], [winter])
) AS pvt

Answer 1

PIVOTS are great, but Conditional Aggregations offer a bit more flexibility and often more performant.
PIVOT
Select *
From (
SELECT State
,B.*
FROM #myTable
Cross Apply (values (concat(season,'_rain'),rain)
,(concat(season,'_snow'),snow)
) B(Item,Value)
) src
Pivot ( sum(value) for Item in ([summer_rain],[summer_snow],[winter_rain],[winter_snow]) ) pvt
Conditional Aggregation
Select State
,[summer_rain] = sum(case when season='summer' then rain end)
,[summer_snow] = sum(case when season='summer' then snow end)
,[winter_rain] = sum(case when season='winter' then rain end)
,[winter_snow] = sum(case when season='winter' then snow end)
From #myTable
Group By State