Possible recursive CTE query using date ranges

Question

Not sure how to even phrase the title on this one!

I have the following data:

IF OBJECT_ID (\'tempdb..#data\') IS NOT NULL DROP TABLE #data
CREATE TA         


        

Answer 1

You don't need a "real" recursive CTE here. You can use one for the month references though:

;WITH Months
as
(
    SELECT DATEADD(day, -DATEPART(day, GETDATE())+1, GETDATE()) as 'MonthStart'
    UNION ALL
    SELECT DATEADD(month, -1, MonthStart) as 'MonthStart'
    FROM Months
)

Then you can JOIN to SELECT TOP 13 * FROM Months in your above query.

I'm not going to try to parse all your CASE statements, but essentially you can use a GROUP BY on the date and the MonthStart fields, like:

GROUP BY Datepart(year, monthstart), Datepart(month, monthstart)

and aggregate by month. It will probably be easiest to have all your options (active, lapsed, etc) as columns and calculate each with a SUM(CASE WHEN ... THEN 1 ELSE 0 END) as it will be easier with a GROUP BY.