Application Item Not Working as Bind Variable in Region Source

Question

I've created an application variable - APP_AC_CODE - a value for which - PA1 - I set as part of the column link on page A that branches to page B.
I use APP_AC_CODE as part of a region title on page B - &APP_AC_CODE. Parameters - which evaluates successfully to 'PA1 Parameters'.
However when I try to use APP_AC_CODE on the same page as part of the SQL query that drives the report for that region it fails to retrieve any records.
If I set the region source to:
SELECT idi FROM v_parameters WHERE aircraft_code = :APP_AC_CODE ;
then it fails but if I explicitly state the where clause:
SELECT idi FROM v_parameters WHERE aircraft_code = 'PA1' ;
then it works just fine and retrieves the records as expected.
If I check the session state then the right value is assigned to APP_AC_CODE; if I check debug then it shows the right value - binding: ":APP_AC_CODE"="APP_AC_CODE" value="PA1". Also, it displays fine as a substitution string.
I'm very confused. I'll be very grateful if someone can shed a little light. I expect I'm doing something stupid - new user and all that - but I haven't got a clue what that is.

Answer 1

Thanks for the reply Scott, but unfortunately I can't upload the app for business reasons. I appreciate that might make it impossible for you to diagnose the problem.
I don't know if I'm making progress with the problem but I've tried adding a hidden page item, setting that value from page A and using it from page B with the same results. Check the session state, the debug messages, or use it as a substitution variable and the right value is there.
I then tried setting the value of the page item with the value of the application item and (according to session and debug) the right value ends up in the page item. Still didn't work though.
I then created a new page (using the sql report wizard in case I was doing something wrong manually) and tried using the application item in the same way with the same problem.
Given that no records are being returned I assume that the database server doesn't care for the SQL query it sees. Is there a way of seeing what this is? When I look at the debug messages, all I see is 'parse query' and 'binding' messages. Any way I can see what the database server eventually sees?
Matt