Reducing Database Call Techniques...query caching the only way?

Query caching is usually the easiest way to implement caching, since it doesn't require any other code changes in most cases. And it's usually good enough that you don't have to chase additional performance (in an intranet app, for example). In addition, it will provide better performance than caching in the session in most cases, unless each user runs a different query in which case it's about the same either way.

But you can do better. You can cache generated HTML in memory or on the filesystem. CF gives you ways to do either, using custom tags like CF_ACCELERATE and built-in tags like CFCACHE, and often that will provide the best performance, since you no longer even have to do the page generation for at least that section of the page.

Honestly, though, if the performance is satisfactory now with query caching, it's probably not worth your while to chase a few additional milliseconds.

Dave Watts, CTO, Fig Leaf Software

What's the most efficient way to reuse data that gets called on practically every page of an application?

That sounds like a question from the certification exam. The answer is to store the data in session or applicaton scope, depending on the circumstances. If the data depends on the user, then the answer is session. If the data persists from user to user, then it is application.

admin portion of the application.

Suggests users must log in. Otherwise you cannot distinguish admin from non-admin.

This will only change whenever a change is made to the page structure in the admin portion of the application.

Then I would go for storing the data in application scope, as the admin determines the value for everybody else. However, the session acope also has something to do with it. Since the changes are only going to occur in the admin portion, I would base everything on a variable, session.role.

You cache the query by storing it directly in application scope within onApplicationStart in Application.cfc, like this:

<cfquery name="application.myQueryName">

</cfquery>

The best place for the following code is within onSessionStart in Application.cfc.

<!--- It is assumed here that login has already occurred. Your code checks whether

session.role is Admin. If so, make the changes. --->

<cfif session.role is 'admin'>

<!--- Make changes to the data in application.myQueryName, otherwise do nothing --->

</cfif>

Added edit: On second thought, the best place for setting the application variable is in onApplicationStart.

That or store the resulting data into an application wide variable scope, such as "Applicaiton" or "Server" or another relevant persistant and shared scope.