Grouping Queries with SV-Semantics in Preference SQL

Preference database queries become more and more important in Data Warehousing or Decision Support Systems. In these environments the standard SQL GROUP BY operation with aggregate functions is extensively used in formulating queries. In this paper, we focus on the novel GROUPING functionality of Preference SQL which substantially extends the common aggregation features of SQL GROUP BY. It fully supports the Substitutable Values semantics for preference queries, enriched by comfortable aliasing mechanisms. This yields to an increased intuitive readability of complex queries, which in turn can reduce clearly the cognitive load for OLAP programmers. In addition we show how a correlated subquery in SQL can be written simpler and evaluated faster using the GROUPING clause.