We provide both MySQL and PostgreSQL databases to suit the different needs of our customers. Here are a few brief notes that may help you decide which one is right for you.
MySQL is the most popular opensource database and it is so common for a number of reasons. It is fast, relatively simple and easy to manage and use. In most cases MySQL will be more than adequate for all your database needs. It is supported by many third party applications you may choose to install (e.g. bulletin boards, guest books, blogs, etc) and is a good choice if you feel ready to begin developing your own database-driven web application. It has an excellent web-based management interface (integrated into the Control Panel)
The smaller hosting plans include only one database but there is no limit to the number of tables inside a database so you can install as many database-driven applications as you'd like even if you have only one database. Please note, however, that as the number of tables inside your database grows it'll get harder to manage that database. Another good point is that if the different applications use separate databases this could lead to improved security.
We have included PostrgeSQL support in our offering for our enterprise customers who need the advanced features that MySQL lacks.
If your web application utilizes foreign key constraints, stored procedures, triggers or more sophisticated SQL statements you should upgrade your account to a hosting plan that includes a PostgreSQL database. If you're not sure what all those mean you can use MySQL instead.