1Department of Math. (Computer Science), Faculty of Science, Alexandria University.
2Department of Math., Faculty of Science, Alexandria University.
* E-mails: y.fouad@sci.alex.edu.eg,
One of the most important problems in relational databases applications like data warehouses is a size of real-world databases. In practical problems, data may contain millions of records in many data tables bounded by relations. One approach to reduce the size of these applications is rough set theory. The Rough set theory is deeply investigated, and an approach for data filtering based on rough set theory is proposed.
In addition, to improve processing of star queries on data and processing of aggregation star queries a new optimization technique is the called pregrouping transformation. Although this transformation is expected to reduce the time needed to answer large aggregation queries to less than 50%, there are several cases where it is not beneficial.
In this paper we retry reach to the optimization case by applying the two above theories.
