I've noodled around with PostGre SQL... wrote a guestbook and gallery in it once. I also took classes in mySQL (And ASP, PHP, Perl, etc). In the end I dumped all SQL stuff from my site, because it proved to be easier to use plain html and notepad for updating. Putting the stuff into Databases is not always easy, and you can feel stuck with a certain data layout and it's tricky to make exceptions for content. You have to think a lot before you can get to work. you have to write secure admin systems. You might fumble and destroy data. Someone else might fumble and destroy the data. Malicious attacks. Must be on a SQL supporting server which makes the site harder to migrate. Imo, SQL is only worth it if you're dealing with large bulks which all look alike more or less (and change a lot).
SQL is not the only choice for databases. You can use XML and XSL in conjunction with PHP I guess. I made some experiments with just XML and XSL, but didn't like. I wish the I could somehow use clientside url vars with HTML, then link to an XSL file for pulling data, and an XML file for the database.
http://web.telia.com/~u48508900/temp/Plain html with div id/class tags almost is like a database if it's written clean enough. Writing a parser for it might not be hard.