Limitations of Relationships Constructed from Coinciding Data
J.H. ter Bekke and J.A. Bakker

Abstract
Partitioning of data with the group by clause is in SQL defined by one or more attributes from a single, possibly derived relation. The language allows therefore groupings defined by compositions of basic and/or referential attributes, i.e. foreign key attributes. However, partitioning applied to a view derived from more than one relation can lead to misinterpretation, ambiguity and/or incomplete results of which examples are shown. We argue that the specification of data aggregated from diverse tables must be based solely on referential attributes. Consequently, if such attributes are absent, the only way to achieve reliable partitioning is to improve the underlying data model by adding structural aggregation. We illustrate this by simple examples using a semantic framework for database design and data manipulation.
Keywords: intelligent databases, SQL, semantic modeling, aggregate query.

Publication Data
Proceedings of the International Conference on Intelligent Systems and Control (ICSC 2001), Clearwater, Florida, pp. 247-252.
Editor: M.H. Hamza
Publisher: ACTA Press, Anaheim - Calgary - Zurich
Year: 2001
ISBN: 0-88986-315-6