In a previous blog entry ( OpenSource Databases. Why did we choose for our project Mysql?), talked about the Open Source databases such as interesting and reliable option for the development of business intelligence projects. We saw some different products and compare between them.
But there are other alternatives (with limitations in most cases) that allow us to start working with "big" of a free. Express versions are called. Versions are designed for small systems, for development work or training, for prototyping or evaluation, that allow us to "initiation" with the great managers of relational databases. In most cases, the product is offered fully functional, but with limitations (the maximum size of the database, use Ram memory or processors of the machine, etc). There may also be features that are not active in these versions (such as partitioning version of Oracle Express). I leave the link to the manufacturers' web sites where you can download these versions: