PostgreSQL - PostgreSQL is a powerful, open source object-relational database system.
Datahike - A durable datalog database adaptable for distribution.
MySQL - The world's most popular open source database
SQLite - SQLite Home Page
Matisse - Matisse is a post-relational SQL database.
Microsoft SQL - Microsoft SQL is a best in class relational database management software that facilitates the database server to provide you a primary function to store and retrieve data.