Relational databases are no longer fashionable, but they are backed by some great theory and they remain very important in commercial practice. Read http://phil

Relational databases are no longer fashionable, but they are backed by some great theory and they remain very important in commercial practice. Read http://philip.greenspun.com/sql/ http://philip.greenspun.com/sql/ for a quick introduction, but use http://www.postgresql.org/ http://www.postgresql.org/ rather than Oracle for the exercises/examples because it's much easier to install. I trust you'll have no shortage of recommendations about CAP, column-based stores, and support for schema flexibility in other comments.