Teaching Structured Design of Network Algorithms in Enhanced Versions of SQL.pdfVIP

Journal of Information Technology Education Volume 3, 2004 Teaching Structured Design of Network Algorithms in Enhanced Versions of SQL Bert de Brock University of Groningen, Groningen, The Netherlands e.o.de.brock@bdk.rug.nl Executive Summary From time to time developers of (database) applications will encounter, explicitly or implicitly, struc- tures such as trees, graphs, and networks. Such applications can, for instance, relate to bills of mate- rial, organization charts, networks of (rail)roads, networks of conduit pipes (e.g., plumbing, electric- ity), telecom networks, and data dictionaries. Algorithms on such data structures often require recur- sion or iteration where the number of repetitions is unknown a priori. Such algorithms are usually implemented in a third generation language (3GL) and, therefore, are typically “record-at-a-time”. A vast amount of theoretical work on recursive queries in logical languages (and related problems in research prototypes) is available, but these “extensions” typically are not available in commercial da- tabase management systems. Hence, they do not directly help the database developer “in the field” who has available only “ordinary” SQL with a few enhancements. Extensions of SQL with assignments and “control of flow” constructions such as the while-loop en- able database developers to manage and solve such graph problems more completely and compactly on a 4GL-level in their daily work. Such SQL-extensions have existed for some time in several com- mercially available database management systems. Incorporating this 4GL-approach in the educa- tional field constitutes a challenge as well as an opportunity, as we show in this paper. We also illus- trate various classical aspects of a