Using an expression in SSRS to display rolling 12 month and year to date volumes

Question

I need some help in writing an expression in SSRS. I have a table that contains date columns and rows that contain different types of data groups. (e.g. total number of items received during the month, total dollars for the month, etc.) I want to add two
new columns to the end of the report that will display a rolling twelve month total for each of the different rows of data. Plus a column that would show year to date totals for the same rows.
I was thinking I could accomplish this by adding expressions for each row in the new 'rolling twelve month' and 'YTD' columns in my report however, I'm not sure how to structure the expressions to achieve this.
Here is an example of how my report currently looks. (I added a pipe delimeter in case the formatting changes once this is submitted.)
                         Jan-2014 | Feb-2014 | Mar-2014 | Apr-2014 | Rolling 12 mth | YTD
Items received     100 | 35 | 45 | 12 | 192 | 192
Dollars                $50.00 | $25.00 | $120.00 | $15.00 | $210.00 | $210.00
Any guidance you can provide would be appreciated.
Thank you  

Answer 1

This example shows how to get what you need. It'll take modifying your query to add two cased columns onto the end.
DECLARE @forumTable TABLE (periodYear INT, periodMonth INT, periodMonthName VARCHAR(12), periodDollars MONEY, periodItems INT)
DECLARE @i INT = 0
SET NOCOUNT ON
WHILE @i < 24
BEGIN
INSERT INTO @forumTable (periodYear, periodMonth, periodMonthName, periodDollars, periodItems)
VALUES (YEAR(DATEADD(MONTH,-@i,GETDATE())), Month(DATEADD(MONTH,-@i,GETDATE())), DATENAME(MONTH,DATEADD(MONTH,-@i,GETDATE())), 1000-@i, 100-@i)
SET @i = @i+1
END
SET NOCOUNT OFF
SELECT *,
CASE WHEN CONVERT(VARCHAR,periodYear) + '-' + CONVERT(VARCHAR,periodMonth) + '-01' > DATEADD(MONTH,-12,GETDATE()) THEN periodItems ELSE 0 END AS ytdItems,
CASE WHEN CONVERT(VARCHAR,periodYear) + '-' + CONVERT(VARCHAR,periodMonth) + '-01' > DATEADD(MONTH,-12,GETDATE()) THEN periodDollars ELSE 0 END AS ytdDollars
FROM @forumTable