Aggregate-Query Processing in Data Warehousing Environments
Ashish Kumar Gupta, Venky Harinarayan, Dallan Quass · 1995
In this paper we introduce generalized pro-jections (GPs), an extension of duplicate-eliminating projections, that capture aggre-gations, groupbys, duplicate-eliminating pro-jections (distinct), and duplicate-preserving projections in a common unified framework. Using GPs we extend well known and simple algorithms for SQL queries that use distinct projections to derive algorithms for queries us-ing aggregations like sum, max, min, count, and avg. We develop powerful query rewrite rules for aggregate queries that unify and ex-tend rewrite rules previously known in the lit-erature. We then illustrate the power of our approach by solving a very practical and im-portant problem in data warehousing: how to answer an aggregate query on base tables using materialized aggregate views (summary tables). 1