MySQL is a relational database system (RDBMS) that runs as a server providing multi-user access to several databases. All major programming languages include libraries to access MySQL. It comes with a command line tool, with many third party graphical user interfaces also available. Although not considered a full enterprise RDBMS like Oracle or PostgreSQL, it supports most RDBMS technologies like foreign keys, triggers, views, indexing, and backup.
MySQL Workbench is an open source, visual based tool for MySQL database design, creation and administration. It is separate from, but connects to MySQL, which is database software built on a version of Structured Query Language or SQL (see MySQL tool description in the DataONEpedia).
The combination of PostgreSQL and PostGIS provides a robust database platform that supports the integrated management of both geospatial data and attributes associated with those data in a database system that is supported by a large number of client applications, including GIS and mapping applications. PostgreSQL is an open source object-relational database server that implements the Structured Query Language (SQL) for database design, management, and use.
The SQL Server is a relational model database server produced by Microsoft that provides a high performance database platform that’s reliable, scalable, and easy to manage. Its primary query languages are T-SQL and ANSI SQL. There are several Editions of the Server available, which differ depending on the services they provide.