Modificato con gli ultimi requisiti.
Il tuo problema è che stai cercando di ottenere il precedente_avg cercando di manipolare QTR e YEAR. Sto usando la funzione RANK, ordinando il modo in cui voglio che i dati siano classificati. Nei join mi sto assicurando che Regione media =Regione precedente e ignorando l'anno dal trimestre precedente potrebbe essere il quarto trimestre dell'anno precedente per l'anno medio Q1; è più pulito in questo modo.
--Build the test table
IF OBJECT_ID('SALES','U') IS NOT NULL
DROP TABLE SALES
CREATE TABLE SALES
(
Region VARCHAR(255)
, Product VARCHAR(10)
, [Year] INT
, QTR INT
, [Month] VARCHAR(19)
, Sales DECIMAL(19,4)
);
INSERT SALES
VALUES
('NORTH', 'P1', 2015, 1, 'JAN', 1000)
,('NORTH', 'P1', 2015, 1, 'FEB', 2000)
,('NORTH', 'P1', 2015, 1, 'MAR', 3000)
,('NORTH', 'P1', 2015, 2, 'APR', 4000)
,('NORTH', 'P1', 2015, 2, 'MAY', 5000)
,('NORTH', 'P1', 2015, 2, 'JUN', 6000)
,('NORTH', 'P1', 2015, 3, 'JUL', 7000)
,('NORTH', 'P1', 2015, 3, 'AUG', 8000)
,('NORTH', 'P1', 2015, 3, 'SEP', 9000)
,('NORTH', 'P1', 2015, 4, 'OCT', 1000)
,('NORTH', 'P1', 2015, 4, 'DEC', 4000)
,('NORTH', 'P1', 2015, 4, 'NOV', 2000)
,('NORTH', 'P3', 2015, 1, 'FEB', 1000)
,('NORTH', 'P3', 2015, 1, 'FEB', 9000)
,('NORTH', 'P3', 2015, 2, 'APR', 2000)
,('NORTH', 'P3', 2015, 3, 'JUL', 8000)
,('NORTH', 'P1', 2016, 1, 'MAR', 3000)
,('NORTH', 'P1', 2016, 1, 'FEB', 1000)
,('NORTH', 'P1', 2016, 1, 'JAN', 2000)
,('SOUTH', 'P1', 2015, 1, 'JAN', 2000)
,('SOUTH', 'P1', 2015, 1, 'FEB', 3000)
,('SOUTH', 'P1', 2015, 1, 'JAN', 4000)
,('SOUTH', 'P2', 2015, 1, 'MAR', 1000)
,('SOUTH', 'P2', 2015, 1, 'JAN', 8000)
,('SOUTH', 'P2', 2015, 1, 'FEB', 9000)
,('SOUTH', 'P2', 2015, 2, 'JUN', 9000)
,('SOUTH', 'P2', 2015, 2, 'MAY', 8000)
,('SOUTH', 'P2', 2015, 2, 'APR', 2000)
,('SOUTH', 'P2', 2015, 3, 'SEP', 4000)
,('SOUTH', 'P2', 2015, 3, 'AUG', 2000)
,('SOUTH', 'P2', 2015, 3, 'JUL', 1000)
,('SOUTH', 'P2', 2015, 4, 'NOV', 2000)
,('SOUTH', 'P2', 2015, 4, 'DEC', 1000)
,('SOUTH', 'P2', 2015, 4, 'OCT', 5000)
,('SOUTH', 'P3', 2015, 3, 'AUG', 9000)
,('SOUTH', 'P3', 2015, 4, 'OCT', 1000)
,('SOUTH', 'P3', 2015, 4, 'NOV', 3000)
,('SOUTH', 'P2', 2016, 1, 'JAN', 2000)
,('SOUTH', 'P2', 2016, 1, 'JAN', 4000);
--CTE TO CAPTURE AVG SALES BY REGION, PRODCUT, YEAR, QTR; OMIT PRODUCT IF YOU WANT STRAIGHT UP QUARTER AVG, REGARDLESS OF PRODCUCT
WITH cteAvgSales AS
(
SELECT Region, Product, [Year], QTR, AVG(Sales) current_avg
, RANK() OVER(ORDER BY Region, Product, [Year], QTR) AS RNK
FROM SALES
GROUP BY Region, Product, [Year], QTR
)
SELECT s.Region, s.Product, s.[Year] AS [year], s.QTR AS [quarter], s.[Month], s.Sales, a.current_avg, p.current_avg AS previous_avg
FROM SALES s
INNER JOIN cteAvgSales a ON a.Region = s.Region
AND a.Product = s.Product
AND a.[Year] = s.[Year]
AND a.QTR = s.QTR
LEFT JOIN cteAvgSales p ON p.Region = a.Region
AND p.Product = s.Product
AND p.RNK=a.RNK-1
ORDER BY s.Region, s.Product, s.[Year], s.QTR
