Approximating the number of unique values of an attribute without sorting

Abstract

Counts of unique values are frequently needed information in database systems. Especially, they are essential in query optimization and physical database design. Traditionally, exact counts were obtained by sorting, which is an expensive operation. In this paper we present three algorithms for counting unique values by probabilistic methods. These… (More)
DOI: 10.1016/0306-4379(87)90014-7

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Cite this paper

@article{Astrahan1987ApproximatingTN, title={Approximating the number of unique values of an attribute without sorting}, author={Morton M. Astrahan and Mario Schkolnick and Kyu-Young Whang}, journal={Inf. Syst.}, year={1987}, volume={12}, pages={11-15} }