This is what I found in the APEX documentation that comes with Oracle 11g, in the chapter describing building a very simple application:

In Region Source, add the following at the end of the existing code:
WHERE nvl(DEPARTMENT_ID,’-1′) = nvl(:P3_DEPARTMENT_ID,’-1′)

This WHERE clause changes the query to display only those employees that belong to the selected department accounting for empty DEPARTMENT_ID as well.

Making sure the database instance couldn’t potentially use an index in DEPARTMENT_ID column? Why on earth would you teach novice APEX developers such a horrible practice?

To me, it’s one more confirmation that Oracle can do an excellent RDBMS, but when it comes to database applications development . . .