To folks writing database-driven reports for the web: Craig Shallahamer shows why you should let the (Oracle) database handle as much of your selection and transformation logic as possible.
Build your own mini-schema and run queries against it. Publish your experiments for your friends to tweak. Or try out the examples from your favorite SQL book without having to build a database first. Works for Oracle, PostgreSQL, MySQL, and SQL Server flavors. Pretty cool!