penjualan rata-rata kuartal dengan penjualan rata-rata kuartal sebelumnya

Diedit dengan persyaratan terbaru.

Masalah Anda adalah Anda mencoba mendapatkan prior_avg dengan mencoba memanipulasi QTR dan YEAR. Saya menggunakan fungsi RANK, mengurutkan seperti yang saya inginkan untuk peringkat data. Dalam gabungan saya memastikan bahwa Wilayah Rata-rata =Wilayah Sebelumnya dan mengabaikan tahun sejak kuartal sebelumnya bisa menjadi Q4 tahun Sebelumnya untuk tahun Rata-rata Q1; lebih bersih dengan cara ini.

    --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