如何在动态日期上显示上一年

Question

I have a database that has customer, product, date and volume/revenue data. I'd like to create two NEW columns to show the previous year volume and revenue based on the date/customer/product.

I've tried unioning two views, one that has dates (unchanged) and a second view that creates a CTE where I select the dates minus one year with another select statement off of that where VOL and REV are renamed VOL_PY and REV_PY but the data is incomplete. Basically what's happening is the PY data is only pulling volume and revenue if there is data in the prior year (for example if a customer didn't sell a product in 2021 but DID in 2020, it wouldn't pull for the VOL_PY for 2020 - because it didn't sell in 2021). How do I get my code to include matches in dates but also the instances where there isn't data in the "current" year?

Here's what I'm going for: [EXAMPLE DATA WITH NEW COLUMNS]

CURRENT YEAR VIEW:

   SELECT
   CUSTOMER
  ,PRODUCT
  ,DATE
  ,VOL
  ,REV
  ,0 AS VOL_HL_PY
  ,0 AS REV_DOLS_PY
  ,DATEADD(YEAR, -1, DATE) AS DATE_PY FROM dbo.vwReporting

PREVIOUS YEAR VIEW:

WITH CTE_PYFIGURES 
     ([AUTONUMBER]
      ,CUSTOMER
      ,PRODUCT
      ,DATE
      ,VOL
      ,REV
      ,DATE_PY
      ) AS 

(
SELECT b.*
     , DATEADD(YEAR, 1, DATE) AS DATE_PY
FROM dbo.basetable b
)

SELECT  
       v.CUSTOMER
      ,v.PRODUCT
      ,v.DATE
      ,0 AS v.VOL
      ,0 AS v.REV
      ,CTE.VOL_HL AS VOL_HL_PY
      ,CTE.REV_DOLS AS REV_DOLS_PY
      ,DATEADD(YEAR,-1,CTE.PERIOD_DATE_PY) AS PERIOD_DATE_PY
FROM dbo.vwReporting AS v
FULL OUTER JOIN CTE_PYFIGURES AS CTE ON CTE.CUSTOMER=V.CUSTOMER AND CTE.PRODUCT=V.PRODCUT AND CTE.DATE_PY=V.DATE 

Answer 1

You need to offset your current year's data to one year forward and then union it with the current data, placing zeroes for "other" measures ( VOL and REV for previous year and VOL_PY and REV_PY for current year). Then do aggregation. This way you'll have all the dimensions' values that were in current or previous year.

with a as (
  select
    CUSTOMER
    , PRODUCT
    , [DATE]
    , VOL
    , REV
    , 0 as vol_py
    , 0 as rev_py
  from dbo.vwReporting

  union all

  select
    CUSTOMER
    , PRODUCT
    , dateadd(year, 1, [DATE]) as [DATE]
    , 0 as VOL
    , 0 as REV
    , vol as vol_py
    , rev as rev_py
  from dbo.vwReporting
)
select
    CUSTOMER
    , PRODUCT
    , [DATE]
    , VOL
    , sum(vol) as vol
    , sum(rev) as rev
    , sum(vol_py) as vol_py
    , sum(rev_py) as rev_py
from a
group by
    CUSTOMER
    , PRODUCT
    , [DATE]
    , VOL