Selecting a column in Answers report based on user prompt/ apply filter

Question

I need to do the following in OBIEE Answers report (version 10.1.3.4.1):
1) Think of a simple table with dim TX_type and some measures like month_jan, month_feb, month_mar
so the fact table looks like (column names) tx_type, month_jan, month_feb, month_mar
2) I need to select the measure column based on a user dashboard prompt, prompt populates a presentation variable var_month = jan or feb or mar
3) I need to select the correct measure (one of these month_jan, month_feb, month_mar) and then apply column filter based on the dim TX_type to split the values of these into multiple columns for report. So the report may look like (in Answers)
Sales , Tax, overheads
where Sales may be defined as sum(month_jan) where rows have TX_type = 'sales'
where Tax may be defined as sum(month_feb) where rows have TX_type = 'tax'
where overheads may be defined as sum(month_mar) where rows have TX_type = 'overheads'
IF the user selects jan
IF user selects Feb then the 3 report columns are based on month_feb and likewise for month_mar
I cannot use column selector option as the report column further apply filter in column filter definitions in Answers...
4) When I try to build the column filter using a presentation variable (var_month), the presentation variable is not getting populated in the column filter.
For e.g. IF var_month = 'jan'
THEN month_jan (let us assume the logical column name is month_jan too)
ELSE month_feb and so on...
However, the var_month always shows 0 in the IF clause. If we used a repository variable instead, it works fine. But since repostory variable cannot be changed on the fly (by user prompt) it is not usable.
We cannot change fact table defintion....and we have 12 measures column and about 8-10 different colum filter based report columns using this measure.

Answer 1

Hi shyamvaran,
have you thought about a SQL statement in the prompt, something like:
SELECT
case when 1=0 then Table."Column" else 'Jan' end
FROM "Subject Area"
union
SELECT
case when 1=0 then Table."Column" else 'Feb' end
FROM "Subject Area"
union
SELECT
case when 1=0 then Table."Column" else 'Mar' end
FROM "Subject Area"
union
SELECT
case when 1=0 then Table."Column" else 'Apr' end
FROM "Subject Area"
etc...
Use this to give you the 12 values for your months then give the prompt column a presentation variable name and set a default value in the 'Default To'. Also set the same default value for the filter.
A couple of points:
1. If you're transforming the presentation variable from 'Jan' to 'month_jan' you may need to edit the syntax for the filter column (not using the dialog box).
2. If you're transforming the behaviour of a dimension / measure column in the report, have you specified the syntax correctly, e.g. sum('@{pres_var}')?
Hope this helps,
Justin