Why (Almost) Every Web Site Needs an RDBMS

When your Web application reaches a certain size, it needs a good database design behind it. And in fact, this 'certain size' is much smaller than almost every small-site developer thinks. Relational Data Base Management Systems (RDBMSes) need not be restrictive or over-architected, as their bad reputation sometimes brings developers to fear. A bit of thought toward what your site does quickly turns into a sensible schema design, and it is easy to leave open expandable storage mechanisms like a configuration table within an RDBMS back end.

Mertz, David. IBM (2007). Articles>Web Design>Server Side Includes>Databases