ADD_MONTHS is SQL function. It will not work.. you need to do something like this..
- Create a calculated column for holding the value of 3 months back month year.
- In the projection filter, you need to use the filter something like CALMONTH = "CALCULATED_CAL_MONTH_3".
- set the formula for CALCULATED_CAL_MONTH_3 similar to this logic.. The below logic is to derive the year, you need to concatenate (using || ) similar logic for month.
if(in(rightstr('$$IP_CALMONTH$$', 2), '01', '02', '03')=1, string(int(leftstr('$$IP_CALMONTH$$', 4))-1), leftstr('$$IP_CALMONTH$$', 4))
The logic checks, if the last 2 chars (month value) is 01, 02, 03 then it will deduct 1 from the year part.. you need to write similar logic to check if month value is in 01, 02, 03, then you need to derive month as (month value + 9), else month value.
Regards,
Ravi