PostgreSQL is powerful and widely compatible, supporting the complete SQL standard, including transactions, foreign keys, ...

In this tutorial, we will step through installing PostgreSQL, connecting to the database, loading some data, and running a variety of SQL queries.

Learn how to use the Azure Portal to create a cloud-based SQL database with just a few mouse clicks.

Here's a quick JDBC with HSQLDB tutorial to get you up and running with Java database connectivity and the popular HyperSQL database.

However, rather than replacing SQL, these databases added their own SQL-like languages that replicated some of the methods and approaches that SQL has ingrained into how developers work.