HTDB can work with or without a database.
when used without a database, the system becomes one of simple document management and retrieval.
when used with a database, then the developer has access to the system's innate
session/user tracking, page logging, performance tracking and other sub-systems
built upon the database layer.
libhtdb uses a simple abstraction layer to talk to the database.
currently, mySql is well supported and is what is running underneath this site.
support for mSql was once well supported, but the layer needs to be re-written,
as recent development has been on the mysql module.
support for Oracle will most probably be next up.
if there is a C language database abstraction library out there that can
be incorporated into htdb, i'd like to hear about it,
as there's no reason this beast couldn't run on top of
Sybase, Informix, etc.