MariaDB is a database server that offers drop-in replacement functionality for MySQL. It is built by some of the original authors of MySQL, with assistance from the broader community. In addition to the core functionality of MySQL, it offers a rich set of feature enhancements including alternate storage engines, server optimizations, and patches.
Nextls is a console application that keeps track of your music collection using a MySQL database to store information such as length, bitrate, metadata, and where on the hard drive it is located. When Nextls is launched, it will figure out any changes done since the previous run and update the database accordingly. The database is very simple to work with, and there also exists a sister project in Nx2 that will allow you to take your database online and stream your music from a Web browser.
libosl, the object storage layer, is a library for storing small to medium-sized data in relational tables. It is easy to use, lightweight, fast, and portable. libosl is suitable for applications that need only a small fraction of the features a full database management system provides.
hamsterdb Embedded Storage is an embedded database engine written in ANSI-C. It includes B+Trees with variable length keys and records. It supports in-memory databases and endian-independent files, database cursors, multiple databases in one file, "record number" databases, and duplicate keys. hamsterdb is very fast and highly configurable. It compiles and runs on Unix platforms, Linux, Microsoft Windows, and Windows CE.
lib4d_sql is a C library that provides the required functions (connect, prepare, execute, etc.) for writing an SQL client for 4D databases. It uses the public 4D SQL protocol, which is supported by 4D products since version 11. It is already used by the PDO_4D Open Source project, and it might be used to provide others drivers for JDBC, ADO, or ActiveRecord.