ConDB is a free open-source convention database system, originally developed for CONduit. It is fairly raw and requires familiarity with Perl, Perl Objects, MySQL, Apache and Unix
MySQL_CBN checks periodically the tables of a MySQL Server. Using the BACKUP, CHECK, OPTIMIZE and ANALYZE, and checks if everything is ok and alert you if anything is wrong.
pgdiff compares the structures of two PostgreSQL databases and returns the differences as a sequence of SQL commands which can be fed to psql to transform the structure of the first to be identical to the second (analagous to diff and patch)
LocalSQL is a local SQL database engine. It is based on the Qt library (for cross-platform tools and GUI support) and the XBase library (for database access).