How to get data occured on less than 12 months gap, please

Question

Hello Good Afternoon,
How can i get ssns that are occured in less than 12 month period
create table #mytemp (SSN varchar(9), planID vcarchar(8), period varchar(7))
Insert Into #mytemp values ('123456789', '200R1','2013-04')
Insert Into #mytemp values ('123456789', '200R5','2014-09')
Insert Into #mytemp values ('123456789', '200R1','2012-05')
Insert Into #mytemp values ('123456789', '200R3','2013-11')
Insert Into #mytemp values ('123456789', '200R1','2014-01')
Insert Into #mytemp values ('213456789', '400R1','2014-04')
Insert Into #mytemp values ('213456789', '400R5','2014-09')
Insert Into #mytemp values ('213456789', '400R1','2013-05')
Insert Into #mytemp values ('213456786', '700R5','2014-05')
Insert Into #mytemp values ('213456786', '400R1','2013-05')
Insert Into #mytemp values ('215556786', '400P1','2013-05')
i am trying to get the below two results
1) How to find out the duplicate SSN's that were having period of less than 12 month difference
2) How to find out the duplicate SSN's that were having period of less than 12 month difference with same planID
Please Help me
expected results for Query 1
create table #ans1 (SSN varchar(9))
Insert Into #ans1 values ('123456789')  --- had more than one record in 12 month span
Insert Into #ans1 values ('213456789')  --  had more than one record in 12 month span
expected results for Query 2
create table #ans2 (SSN varchar(9))
Insert Into #ans2 values ('123456789')  --- had more than one record in 12 month span for plan 200R1
Please help me here with your valuable advise
Thank you in Advance
Milan

Answer 1

1) How to find out the duplicate SSN's that were having period of less than 12 month difference
2) How to find out the duplicate SSN's that were having period of less than 12 month difference with same planID
Below is one method.  The second query also returns '213456789' because your sample data has more than one row for planID 400R1 within 12 months.
SELECT DISTINCT
a.SSN
FROM #mytemp AS a
WHERE EXISTS ( SELECT *
FROM #mytemp AS b
WHERE b.SSN = a.SSN
AND CAST(b.period + '-01' AS date) > CAST(a.period
+ '-01' AS date)
AND CAST(b.period + '-01' AS date) < DATEADD(YEAR, 1,
CAST(a.period
+ '-01' AS date)) );
SELECT DISTINCT
a.SSN
FROM #mytemp AS a
WHERE EXISTS ( SELECT *
FROM #mytemp AS b
WHERE b.SSN = a.SSN
AND b.planID = a.planID
AND CAST(b.period + '-01' AS date) > CAST(a.period
+ '-01' AS date)
AND CAST(b.period + '-01' AS date) < DATEADD(YEAR, 1,
CAST(a.period
+ '-01' AS date)) );
Dan Guzman, SQL Server MVP, http://www.dbdelta.com