How to update sales of last 3 months only

Question

I have a query which basically updates the sales for the whole year, but i just want that one to be changed such that it only updates for the past 3 months,irrespective
of the year ( i mean to say if i run it today it must update march,april,may of 2014 but if i run it on jan 2015 then it must update oct,nov,dec of 2014).
Below is my update statement
update tODS_GLBalance
set tODS_GLBalance.tUTL_JobLogging_Key = @tUTL_JobLogging_Key,
tODS_GLBalance.Balance = vODS_GLBalance.GLAmount,
tODS_GLBalance.ModifiedDate = GETDATE(),
tODS_GLBalance.ModifiedUser = SUSER_NAME()
From ODS.Staging.vODS_GLBalance
Left Outer Join Ods.JJill.tODS_GLBalance
ON tODS_GLBalance.FiscalYearId = vODS_GLBalance.FiscalYearId
AND tODS_GLBalance.FiscalMonthOfYearId = vODS_GLBalance.FiscalMonthOfYearId
AND tODS_GLBalance.Page = vODS_GLBalance.PAGE
Where
tODS_GLBalance.FiscalYearId = YEAR(GETDATE())
AND
tODS_GLBalance.FiscalMonthOfYearId = vODS_GLBalance.FiscalMonthOfYearId
AND tODS_GLBalance.FiscalYearId = vODS_GLBalance.FiscalYearId
AND tODS_GLBalance.Page = vODS_GLBalance.Page
AND tODS_GLBalance.Balance <> vODS_GLBalance.GLAmount
Can someone please help me with this, Please let me know if you have any questions or if i am unclear.
Thanks

Answer 1

I suggest adding this line of code to the where clause:
AND
tODS_GLBalance.FiscalMonthOfYearId
in(month(dateadd(m,-1,getdate())),month(dateadd(m,-2,getdate())),month(dateadd(m,-3,getdate())))
This assumes that you are testing against the fiscalmonthofyear and that the fiscal periods are the same as calendar periods. Otherwise, there will be some adjusting to do.
This is basically checking to see if the fiscal monthofyearid is in the 3 most recent months.
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