I am looking for a good book on the math and/or theory behind relational databases and associated topics.. I am looking some works on set theory, algebra, or any other books/papers on the mechanics that databases are built on. I found one book online, http://web.cecs.pdx.edu/~maier/TheoryBook/TRD.html, The Theory of Relational Databases by David Maier and that is what got me interested in the foundations of database design and theory.