Issues in System Variable in BI Publisher

Hello,

I have been using :xdo_user_name for displaying the user name. The system variable is running successfully in following command-

select "PAN_TM_JURISDICTION_HRCHY"."AREA_CD" as "CCIT" from "APPDB"."PAN_TM_JURISDICTION_HRCHY" "PAN_TM_JURISDICTION_HRCHY" where "PAN_TM_JURISDICTION_HRCHY"."CCIT_BLDG_ID"= :xdo_user_name

But when I use the same query in Case Statement, then the system variable doesn't work. The query used is:-

select unique case

when "PAN_TM_JURISDICTION_HRCHY"."CCIT_BLDG_ID"=:xdo_user_name

then

("PAN_TM_JURISDICTION_HRCHY"."AREA_CD")

end

from "APPDB"."PAN_TM_JURISDICTION_HRCHY" "PAN_TM_JURISDICTION_HRCHY"