Where can I learn about the different types of databases?

I am looking into creating a web application that will make heavy use of a database to store data about the different users. Problem is, I don't really know that much about databases, especially in an environment that will (hopefully) have lots of traffic.

I have used MySQL before for some basic websites (college clubs, blog, low traffic stuff), but ha开发者_开发知识库ve heard this isn't a good choice for a real application.

Where can I learn more about the different databases out there? I have tried Google and Wikipedia, but there is just so much information I don't know where to start...

Write down your application's functional and non-functional requirements. Translate these into the conditions that the database must satisfy. Then match those with the readily available lists of features.

MySQL is used as a backend database on some large web sites.

(My preference is SQL Server, but it's not free like MySQL...)