Question

Okay, I feel like I should be able to do this, but I have searched to no avail.

I need to show one of two different data sets depending on what day of the year it is. Specifically, if today is October 31 (or earlier,) I want to pull all entries from October 1 of last year to the end of current year. If today is after October 31, I want my data set to show entries from October 1 of the current year to the end of next year.

The code below is creating a simple “calendar” table variable that is storing all the months that exist in a specific dataset. Right now I am just limiting it to dates for current year. I would like to replace that with code to allow it to function as I stated above. I thought of using an IF statement, but I cannot figure out how to compare with getdate() day and month only.

DECLARE @calendar TABLE 
(       mon_name    VARCHAR(10)
    ,   mon_number  INT
    ,   yr          INT
)

INSERT INTO @calendar
SELECT      DATENAME(m,departure_date)
        ,   MONTH(departure_date)
        ,   YEAR(departure_date)
FROM        trip_mission
WHERE       departure_date          <>'1/1/1900' 
AND         YEAR(departure_date)    = YEAR(getdate())
GROUP BY    DATENAME(m,departure_date)
        ,   MONTH(departure_date)
        ,   YEAR(departure_date)

A simplified form of the question may be how can I run some code only if today is <= October 31. It would be super easy if I could say <= October 31, 2012, but I need it to be dynamic so that it will flip over every year.

Answer 1

The following little trick will allow you to select different subsets based on what month it is:

WHERE departure_date >= DATEADD(
  YEAR,
  MONTH(GETDATE()) / 11 - 1,
  CAST(YEAR(GETDATE()) AS char(4)) + '1001'
)

The last argument forms the date of the 1st of October of the current year. The second argument controls whether we subtract 1 year or not. Assuming the current year to be 2012, here’s what we get depending on the current month

Current month  MONTH(GETDATE())  MONTH(…) / 11  MONTH(…) / 11 - 1  DATEADD(…)
-------------  ----------------  -------------  -----------------  ----------
January        1                 0              -1                 2011-10-01
February       2                 0              -1                 2011-10-01
March          3                 0              -1                 2011-10-01
April          4                 0              -1                 2011-10-01
May            5                 0              -1                 2011-10-01
June           6                 0              -1                 2011-10-01
July           7                 0              -1                 2011-10-01
August         8                 0              -1                 2011-10-01
September      9                 0              -1                 2011-10-01
October        10                0              -1                 2011-10-01
November       11                1              0                  2012-10-01
December       12                1              0                  2012-10-01