SQL Server: get all previous values that are within half year of a month (not in future)?

Question

I have values such as

201401
201411
201501
201504
201508
201606

If I select values last six months from 201501, I want to get 201411. If last six months from 201606, then nothing. If from 201508, then 201504.

I have a month column of the varchar form 201601.

How can I get the last six months relative to each month with some datatype objects such as datepart functions?

Answer 1

Another option which will reduce record level processing/conversions

Declare @YourTable table (SomeCol varchar(6))
Insert Into @YourTable values
(201401),
(201411),
(201501),
(201504),
(201508),
(201606)

Declare @Target varchar(6) = '201508'

Select *
 From  @YourTable
 Where SomeCol >= format(dateadd(MONTH,-6,cast(@Target+'01' as date)),'yyyyMM') 
   and SomeCol < @Target

Returns

201504