%0 Journal Article
%T An Efficient Algorithm for Processing Multi-Relation Queries in Relational Databases
%A Liu
%A Weiyi
%J 计算机科学技术学报
%D 1990
%I 
%X After a relation scheme R is decomposed into the set of schemes ρ={R1，…，Rn},we may pose queries as if Rexisted in the database,taking a join of Ri‘s,when it is necessary to implement the query,Suppos a query involves a set of attributes S R，we want to find the smallest subset of ρ whose union includes.S.We prove that the problem is NP-complete and present a polynomial-bounded approximation algorithm.A subset of ρ whose union includes S and has a decomposition into 3NF with a lossless join and preservation of dependencies in given in the paper.
%K 相关数据库
%K 多相关询问
%K 有效算法
%U http://www.alljournals.cn/get_abstract_url.aspx?pcid=5B3AB970F71A803DEACDC0559115BFCF0A068CD97DD29835&cid=8240383F08CE46C8B05036380D75B607&jid=F57FEF5FAEE544283F43708D560ABF1B&aid=AB68D885EA9BEAA96B836B3CA204B4B4&yid=8D39DA2CB9F38FD0&vid=94C357A881DFC066&iid=38B194292C032A66&sid=FBCA02DBD05BD4EA&eid=C812B90E96151014&journal_id=1000-9000&journal_name=计算机科学技术学报&referenced_num=0&reference_num=0