Name: PostgreSQL
Website: www.postgresql.org
Description:

For more than 15 years, PostgreSQL has continued to establish itself as a provider of data development for various users and architecture which is reliable and accurate.

PostgresSQL is a powerful, open source object-relational database which runs on major operating systems like Linux and Windows.

As an enterprise class database, PostgresSQL offers Multi-Version Concurrency Control, tablespaces, asynchronous replication, online/hot backups, multiple character encoding, and other sophisticated features.

They also take pride in their standard compliance with Data Integrity features that include foreign keys with restricting and cascading updates/deletes, primary keys, unique constraints and not null constraints, as well as check constraints.