On the size of projections: I
type: Item
instance of: scholarly article
title: On the size of projections: I
zbMATH Open document ID: 0535.68048
DOI: 10.1016/0020-0190(82)90134-X
author: Erol Gelenbe
author: Danièle Gardy
published in: Information Processing Letters
publication date: 1982-01-01T00:00:00Z
review text: The paper deals with the problem of estimating the number of distinct 'rows' in the projection of a 'table' onto a subset of its 'columns' (the words marked by apostrophes roughly stand for 'tuples', 'relation', 'attributes' respectively, in the usual relation model). The number of tables whose projection along one column contains exactly a given number of rows, is found; hence, the probability that the projection will have a fixed number of rows; a similar approach is undertaken for the case where the projection is to be made onto more columns. Finally, more computationally efficient forms of these results are discussed.
reviewed by: H. Luchian
Mathematics Subject Classification ID: 68P20
zbMATH DE Number: 3850500
zbMATH Keywords: data base operations
zbMATH Keywords: projection
zbMATH Keywords: table
zbMATH Keywords: relational data base
zbMATH Keywords: relation model
Wikidata QID: Q56992526
MaRDI profile type: Publication
full work available at URL: 0020-0190(82)90134-x
OpenAlex ID: W2021705190
description: scientific article; zbMATH DE number 3850500