Why parameterize reports?

This is a very important question to ask ourselves, and while the answer might seem obvious, it goes a little deeper. Imagine that we are a report developer for a large organization with several different departments. Now we create a report for a department that shows their costs for the fiscal quarter—that's great. Now a second department asks us to create the same report for them. Then a third department asks for a similar report, but they want to be able to see data for both last quarter and this quarter. By this time, we have created three similar reports, each representing the same set of data and running the same queries, only that we have hard coded the department information. Now we have to maintain all three of those reports, and any changes or mistakes we or an analyst find in any of the reports, ultimately we will ultimately have to fix in all three reports.

The solution to this problem is to parameterize our report. In a simple scenario such as this...