[basetop]

With databases or anything in general, I believe in doing first and then learning the principles.

Play around with a small RDBMs like sqlite. Do a project around it. Look at the source maybe and then learn about the principles. Foundations of databases are based on discrete mathematics ( where relational comes from in RDBMs ) so a background in discrete math helps.

For enterprise level stuff ( clustering, replication, distribution, etc ), it's more practical to learn on the job where you have access to the hardware, servers, etc.