sqlect previous month using yyyymm in SQL

Hi All
Quick question, I would like to know who you select the previous month in SQL Server when using a YYYYMM int format.
i.e. I have a date in my date_dim that is 201504 and I want it to become 201503 in my results.
is there a quick method of doing thisd as the only method I currently have is very long winded and will slow my code?
I'm sure this is a simple fix but need some assistance with it...Thanks.
twfw123Asked:
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Ryan ChongBusiness Systems Analyst , ex-Senior Application EngineerCommented:
try:

SELECT convert(varchar(6),convert(datetime, concat('201504','01'), 112)-1,112)
Scott PletcherSenior DBACommented:
SELECT date_dim - CASE WHEN date_dim % 100 > 1 THEN 1 ELSE 89 END AS date_dim_minus_1

For example:
SELECT date_dim, date_dim - CASE WHEN date_dim % 100 > 1 THEN 1 ELSE 89 END AS date_dim_minus_1
FROM (
    SELECT 201403 AS date_dim UNION ALL
    SELECT 201412 UNION ALL
    SELECT 201401
) AS test_data

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Microsoft SQL Server 2008

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