Concatenating Numbers Together in Oracle APEX using SQL

Ok. Here is some background: I have created a simple APEX application that is going to replace a handful of static HTML pages, an Access Database, and LOTS of manual work. Users use the application to submit work requests to my team and upon submission of the form the information is presented back to them in a 'receipt' with a new 'Request #' which they can use k开发者_Python百科ind of like a UPS tracking number to make inquiries of their project. This number is the primary key of the submitted table and is auto-incremented by a sequence. This all works perfectly so far.

My problem is that for auto-incrementing to work, my PK obviously has to be a 'Number'. Again not really a problem. The issue is that prior to migrating to the APEX tool our 'Request #s' were formatted as a string of numbers 8 digits long with the necessary number of zeros (0's) to the left of the actual number. So Request # 789 is actually stored as 00000789 in our Access database. My boss has indicated that this same format needs to be mimicked when the # is displayed in the APEX tool as well since that is what our clients are used to seeing.

I need the Request # to continue to be stored as a Number so that I can continue to auto-increment but I need to find some way to append/concatenate the appropriate number of 0's to the front of the number when it is displayed. This is will likely need to be done with SQL. I am currently using this simple SQL script to display the #:

SELECT req_num
FROM proj_apex
WHERE req_num = (SELECT MAX(req_num) FROM proj_apex)

Thoughts? Any APEX or SQL developers have ideas?

select to_char(req_num, '00000009') ...

http://www.techonthenet.com/oracle/functions/to_char.php