PostgreSQL - PostgreSQL is a powerful, open source object-relational database system.
Amazon RDS - Easy to manage relational databases optimized for total cost of ownership.
MySQL - The world's most popular open source database
Microsoft Azure SQL Database - Azure SQL Database lets you create, extend and scale relational applications into the cloud.
MariaDB - An enhanced, drop-in replacement for MySQL
Google Cloud SQL - Google Cloud SQL is a fully-managed database service that makes it easy to set-up, maintain, manage and administer your MySQL database.