Queries with Difference on Probabilistic Databases
Document Type Conference Paper
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We study the feasibility of the exact and approximate computation of the probability of relational queries with difference on tuple-independent databases. We show that even the difference between two \safe" conjunctive queries with- out self-joins is \unsafe" for exact computation. We turn to approximation and design an FPRAS for a large class of relational queries with difference, limited by how difference is nested and by the nature of the subtracted subqueries. We give examples of inapproximable queries outside this class.
Date Posted: 24 July 2012