LogiQL

"I gladly recommend the LogiQL book to anyone interested in databases. ... The book is easy to read, contains many examples and exercises, and offers teachers involved in databases and their applications a very effective tool to get students to understand databases and how to program them."
-Dr. Herman Balsters, Associate Professor of Information Systems Design and Former Program Director of the Interfaculty of Industrial Engineering, University of Groningen

"The first mistake people will make is to think that LogiQL is another SQL. No, no. SQL is for accessing data and maintaining data integrity in a relational model. LogiQL discovers and deduces logical relations from predicates by looking at data and a set of predicates that define rules. If you ever worked with the Prolog language, then you know the difference.
LogiQL has an extensional database (EDB) and intentional database (IDB). EDB predicates normally are used to hold the facts that you explicitly enter into the workspace. In contrast, the facts populating IDB predicates are computed for you by your logic program. Think of SQL as a library and LogiQL is the research librarian.
This is the only book on LogiQL and it is designed as a textbook with examples and tests for someone who wants to learn this tool. Get the software, open the book, and get started."
-Joe Celko, Independent Database Consultant