Containment of Aggregate Queries

摘要: The problem of deciding containment aggregate queries is investigated. Containment reduced to equivalence for with expandable aggregation functions. Many common functions, such as max, cntd (count distinct), count, sum, avg, median and stdev (standard deviation) are shown be expandable. It that even in the presence integrity constraints, can equivalence. For conjunctive count sum-queries, simpler characterizations given, do not require checking These results built upon order solve finding maximally-contained sets rewritings count-queries.