This volume is a collection of the most important contributions presented at the second MFDBS conference held in Visegrád, Hungary, June 26-30, 1989. The papers selected from more than one hundred submissions, originating from 23 countries in 4 continents, can be roughly divided into the following sections: theoretical fundamentals of relational databases, logical foundations and databases, data modelling, database design, deductive databases, transaction management and security, concurrency control and distributed databases. The volume reflects the current state of knowledge and is a guide to further development in database theory.