Alternative to using CASE in a GROUP BY - sql

Question

I am trying to find a more compact code form and faster way to execute a query that requires (or at least I think requires) grouping by TWO case statements
I've tried using OVER PARTITION but can't seem to get the desired result
SELECT
CASE
WHEN AA.BUSINESS_SEGMENT LIKE 'YEPPERS%'
THEN 'YES'
ELSE 'NO'
END 'YZY',
CASE
WHEN MONTH(POI.EX_FACTORY_DATE) >= 1 AND MONTH(POI.EX_FACTORY_DATE) <=3
THEN
'Q1'
WHEN MONTH(POI.EX_FACTORY_DATE) >= 4 AND MONTH(POI.EX_FACTORY_DATE) <=6
THEN
'Q2'
WHEN MONTH(POI.EX_FACTORY_DATE) >= 7 AND MONTH(POI.EX_FACTORY_DATE) <=9
THEN
'Q3'
WHEN MONTH(POI.EX_FACTORY_DATE) >= 10 AND MONTH(POI.EX_FACTORY_DATE) <=12
THEN
'Q4'
END 'QTR',
SUM(POI.PO_ORDERED_QUANTITY) PO_QTY
FROM VW_PO_ITEM POI
LEFT JOIN VW_ARTICLE_ATTRIBUTES AA ON AA.ARTICLE = POI.MATERIAL
WHERE POI.DEL_INDICATOR <> 'L' AND POI.EX_FACTORY_DATE BETWEEN '7/1/2019' AND '12/31/2019' AND ((POI.SHIPPING_INSTRUCT='A2' AND AA.BUSINESS_SEGMENT NOT LIKE 'YEPPERS%') OR AA.BUSINESS_SEGMENT LIKE 'YEPPERS%')
GROUP BY
CASE
WHEN AA.BUSINESS_SEGMENT LIKE 'YEPPERS%'
THEN 'YES'
ELSE 'NO'
END,
CASE
WHEN MONTH(POI.EX_FACTORY_DATE) >= 1 AND MONTH(POI.EX_FACTORY_DATE) <=3
THEN
'Q1'
WHEN MONTH(POI.EX_FACTORY_DATE) >= 4 AND MONTH(POI.EX_FACTORY_DATE) <=6
THEN
'Q2'
WHEN MONTH(POI.EX_FACTORY_DATE) >= 7 AND MONTH(POI.EX_FACTORY_DATE) <=9
THEN
'Q3'
WHEN MONTH(POI.EX_FACTORY_DATE) >= 10 AND MONTH(POI.EX_FACTORY_DATE) <=12
THEN
'Q4'
END
--desired result (the query above does produce this)
YZY QTR PO_QTY
-------- ---- ---------------------------------------
NO Q4 389309
YES Q4 649842
YES Q3 843438
NO Q3 20146

Answer 1

I think better is use DATEPART(quarter
FROM MyTable
GROUP BY DATEPART(quarter, columndate)

Answer 2

Consider a CTE to handle unit level calculation before final aggregation, avoiding repetition. Also, look into DatePart to extract date parts from datetime fields:
WITH cte AS (
SELECT CASE
WHEN AA.BUSINESS_SEGMENT LIKE 'YEPPERS%'
THEN 'YES' ELSE 'NO'
END [YZY],
DATEPART(qq, POI.EX_FACTORY_DATE) AS [QTR],
POI.PO_ORDERED_QUANTITY
FROM VW_PO_ITEM POI
LEFT JOIN VW_ARTICLE_ATTRIBUTES AA
ON AA.ARTICLE = POI.MATERIAL
WHERE POI.DEL_INDICATOR <> 'L'
AND POI.EX_FACTORY_DATE BETWEEN '2019-07-01' AND '2019-12-31'
AND (
(POI.SHIPPING_INSTRUCT='A2'
AND AA.BUSINESS_SEGMENT NOT LIKE 'YEPPERS%')
OR
AA.BUSINESS_SEGMENT LIKE 'YEPPERS%'
)
)
SELECT [YZY], [QTR],
SUM(POI.PO_ORDERED_QUANTITY) AS PO_QTY
FROM cte
GROUP BY [YZY], [QTR]