To me they are unrelated and HTML5 does not deal with databases. HTML is a language for presenting content. HTML5 has added new features related to semantics, media presentation, and some browser manipulation (like history). http://diveintohtml5.info/ is a great website to learn about the new features in HTML5, and some possible applications in website development.
HTML does not discriminate with regards to content, and doesn't care whether it comes from a database or if you input it by hand. It will treat that content the same.
PHP is an example of a language that interacts with a database.