This section lists a few resources to learn about datalog.
Stefano Ceri, Georg Gottlob, Letizia Tanca. What you always wanted to know about Datalog (and never dared to ask) (1989) Available online at https://ieeexplore.ieee.org/document/43410
Serge Abiteboul, Richard Hull, Victor Vianu. Foundations of databases (1995) Addison Wesley. Available online at http://webdam.inria.fr/Alice/
Jeffrey D. Ullman. Principles of database and knowledge-base systems Vol. I and Vol. II (1988) Computer Science Press Inc.