Subtract month from yearmonth

Question

In SQL I have a criteria to subtract one month from the YYYYMM value. Kindly help me. I able to get answer with below

select 201608 - 1;

But when it is 01 month, It doesn't works.

Help me on this, without checking 01 month in if condition !

I also went through DATADD and DATEDIFF functions, but couldn't able to get results as expected

Answer 1

Select DateAdd(MM,-1,cast(cast(201608 as varchar(10))+'01' as date))

返回2016-07-01的日期

Answer 2

SQL contains date manipulation functions. Use those:

SELECT DATEDIFF(DAY, DATEADD(day, -1, @dateToCheck), GETDATE())

Answer 3

Alternatively you can use some math to convert int into base 12 int , substract month and return back to original encoding.

select d, m, res=(dd/12)*100 + dd%12 + 1
from (
  select *, (d/100)*12 + d%100  - 1 - m as dd
  from ( --sample data, m = months to substract
     values 
      (201608, 10), (201608, 2), (201601, 1), (201601, 12)
    ) t(d,m) 
  ) t