With today's zippier hardware, though, most small-scale applications can use very simple methods and still achieve adequate performance. It's difficult to jump into Oracle, say, while also learning AOLserver or Tcl. Oracle's documentation and technical support, while improving with each release, are generally uninviting. You're ready for a dynamic project that involves data concurrency, report generation, and perhaps distributed scalability. Then choose either to download PostgreSQL or buy Oracle, and also whether to teach yourself SQL or take a database class.
Special situations call for special database choices.
The four scenarios above, though, cover the majority of decisions you'll face, and also hint at the proper way to think about DBMS strategy. Suppose Siegfried in Stuttgart is paying 10 cents a minute for local phone service to connect his 56 K modem. He likes the way that your home page looks, but he doesn't want to read it while paying the phone company's rates. With the average corporate site, this would be 30 or 40 pages that could all be downloaded within a few minutes. This would be fine for AOLserver, except that some of these robots seem to aim for breadth-first searching.