Check the below input data and expected output to generate the report on missing Year – Month data.

Input Data:

YearMonthCol
------------
201501
201506
201601
201608
201702
201704

Expected Data:

AllMonths
---------
2017-04
2017-03
2017-02
2017-01
2016-12
2016-11
2016-10
2016-09
2016-08
2016-07
2016-06
2016-05
2016-04
2016-03
2016-02
2016-01
2015-12
2015-11
2015-10
2015-09
2015-08
2015-07
2015-06
2015-05
2015-04
2015-03
2015-02
2015-01

Create a table with sample data:

CREATE TABLE Dates 
(YearMonthCol INT)
GO
 
INSERT Dates 
VALUES
('201501')
,('201506')
,('201601')
,('201608')
,('201702')
,('201704')
GO

Solution:

;WITH CTE AS 
( 
    SELECT CAST ( LEFT(YearMonthCol,4) + '/' + RIGHT(YearMonthCol,2) + '/' + '01' AS VARCHAR(10)) YearMonthCol ,ROW_NUMBER() OVER ( ORDER BY YearMonthCol ) 
    ranker FROM Dates 
) 
,CTE1 AS
(  
    SELECT c1.YearMonthCol, CAST ( '<x>' + CAST(c1.ranker AS VARCHAR(10)) + '</x>' AS XML ) ranker,c1.ranker rnk 
    ,ISNULL(c2.YearMonthCol,c1.YearMonthCol) YearMonthEnds 
	FROM CTE c1 
    LEFT JOIN CTE c2 
	ON c1.ranker = c2.ranker - 1 
)
,CTE2 AS
( 
    SELECT *, DATEDIFF ( M ,YearMonthCol, YearMonthEnds )  diff , CAST ( REPLICATE( CAST ( ranker AS VARCHAR(10)) + ',' , 
    CASE WHEN DATEDIFF ( M ,YearMonthCol, YearMonthEnds ) > 1     THEN  DATEDIFF ( M ,YearMonthCol, YearMonthEnds ) ELSE 1 END ) AS XML ) xmlcol FROM CTE1 ) 
    SELECT CONVERT(Varchar(7),DATEADD(m,RowNumber,YearMonthCol),121) as AllMonths FROM CTE2 s
CROSS APPLY
(
     SELECT project.D.value('.','VARCHAR(50)') as SplitData,ROW_NUMBER() OVER(Partition by Project.D.value('.', 'varchar(50)') ORDER BY (SELECT NULL)) -1 as RowNumber   
     FROM s.xmlcol.nodes('x') as project(D)
) t 
ORDER BY AllMonths DESC

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