Three of the most popular database servers are MySQL, PostgreSQL, and Firebird. The features of these open source relational database management systems (RDBMS) are summarized below.

MySQL

MySQL is one of the most widely used open source SQL RDBMS. MySQL AB, a for-profit company, developes, distributes, and supports this system. MySQL's source code is available under the GNU GPL terms. The project's source code is also under various proprietary agreements.

MySQL boasts scalability and flexibility. This system runs anything such as massive data warehouses that hold terabytes of information or deeply embedded applications that have a 1MB footprint. It is also lauded for its high performance. MySQL features Table and Index Partitioning, full-text indexes, distinctive memory caches, ultra-fast load utilities, and many more.

The system has high availability. It runs high-speed master-slave replication configurations with Hybrid and Row-Based Replication. In addition, it also has special Cluster servers that offer instant failover. MySQL has strong data protection. It has powerful mechanisms to ensure only authorized users have access. It also has powerful data encryption and decryption utility. MySQL also features SSH and SSL for supporting secure and safe connections.

PostgreSQL

Released under a BSD-style license, PostgreSQL is one of the technology leaders and one of the world's best open source database. It has excellent record of reliability, outstanding performance, and is very rich in features. With its ease of use, everyone can learn and manage this system without much difficulty. This RDBMS is designed for large and small applications. Whether for data warehousing or transaction processing, PostgreSQL is one of the best solutions.

PostgreSQL has excellent SQL support that includes views, triggers, transactions and sub-transactions, sub-queries, referential integrity, cursors, prepared queries, and functions/stored procedures. Other highlights are replication, high availability, online backup, analysis and monitoring tools, and tablespaces. Here are some other features of PostgreSQL: GUI development environments, support for all major languages and platforms, and two-phase commit.

Firebird

Firebird is also an RDBMS that runs on Windows, Linux, and various Unix platforms. The database is a fork of Borland's InterBase open source edition in 2000. Since Firebird 1.5, however, the source code has been mostly rewritten.

Highlights of the Firebird include: full support for triggers and stored procedures, referential integrity, full ACID compliant transactions, a very small footprint, Multi Generational Architecture (also called MVCC), and External Function support. Firebird also features third party tools such as replication tools and GUI administrative tools.

Firebird 2.5 is still in development, and with a release scheduled this, expect more attractive and practical features.