YrMo Sql

I have created the below query to capture the 1st day of the month for the data that i have archived.  

sELECT Distinct CAST(CAST(YEAR(Archived) AS VARCHAR(4)) + RIGHT('0' + CAST(DATEPART(MM, Archived) AS VARCHAR(12)),2) AS INT) as 'ArchivedYrMo' FROM [RCSC].[dbo].[IAQ_Archive] I
ORDER BY I.Archived DESC

ArchivedYrMo

201311
201310
201309
201308
201307
201306


However I also need to create a query pull the previous month.  I would need the results to pull 201310 if i were running the query today and if i was to run the query in Jan  the results would need to be 201312.

Any takers
Thomask23Asked:
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Scott PletcherConnect With a Mentor Senior DBACommented:
SELECT Distinct
    CAST(CONVERT(char(6), Archived, 112) AS int) AS 'ArchivedYrMo'
FROM [RCSC].[dbo].[IAQ_Archive] I
WHERE
    Archived >= DATEADD(MONTH, DATEDIFF(MONTH, 0, GETDATE()) - 1, 0) AND
    Archived < DATEADD(MONTH, DATEDIFF(MONTH, 0, GETDATE()), 0)
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Jim HornMicrosoft SQL Server Developer, Architect, and AuthorCommented:
>I have created the below query to capture the 1st day of the month
>201311 .. 201310
The above returns year-months, and not days.

If it helps, I have an article out there titled Date Fun, Part One:  Build your own SQL calendar table to perform complex date expressions that is a T-SQL demo on how to build your own calendar table, that can answer questions like 'what is the previous month' very easy.
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Scott PletcherSenior DBACommented:
If you want to return the first of a month, the calc is:

DATEADD(MONTH, DATEDIFF(MONTH, 0, <date>, 0)

There is no I/O and no string conversion, so it's almost no overhead and lightening quick.

As an example, the last three months, grouped by month:

SELECT
    DATEADD(MONTH, DATEDIFF(MONTH, 0, Archived, 0) AS ArchivedYrMo,
    SUM(...),
    COUNT(...)
FROM [RCSC].[dbo].[IAQ_Archive] I
WHERE
    Archived >= DATEADD(MONTH, DATEDIFF(MONTH, 0, GETDATE()) - 3, 0) AND
    Archived < DATEADD(MONTH, DATEDIFF(MONTH, 0, GETDATE()), 0)
GROUP BY
    DATEADD(MONTH, DATEDIFF(MONTH, 0, Archived, 0)
0
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