Translating and Optimizing SQL Queries Having Aggregates.

Günter von Bültzingsloewen: Translating and Optimizing SQL Queries Having Aggregates. VLDB 1987: 235-243

@inproceedings{DBLP:conf/vldb/Bultzingsloewen87,
  author    = {G{\"u}nter von B{\"u}ltzingsloewen},
  editor    = {Peter M. Stocker and
               William Kent and
               Peter Hammersley},
  title     = {Translating and Optimizing SQL Queries Having Aggregates},
  booktitle = {VLDB'87, Proceedings of 13th International Conference on Very
               Large Data Bases, September 1-4, 1987, Brighton, England},
  publisher = {Morgan Kaufmann},
  year      = {1987},
  isbn      = {0-934613-46-X},
  pages     = {235-243},
  ee        = {db/conf/vldb/Bultzingsloewen87.html},
  crossref  = {DBLP:conf/vldb/87},
  bibsource = {DBLP, http://dblp.uni-trier.de}
}

Abstract

In this paper, we give a precise definition of the semantics of SQL queries having aggregate functions, identify the problems associated with the optimization of such queries and give some solutions. The semantics of SQL queries is defined by translating them into expressions of an extended relational calculus (extensions are necessary for a correct treatment of aggregate functions and null values). The discussion of the optimization problems is based on a new transformation of a relational calculus expression into relational algebra. By investigating the transformation of aggregate functions we are able to identify two major problems: correct integration of the values of aggregate functions applied to empty relations and unnecessary computation of unneeded function values. To solve these problems we propose to interpret an aggregate function applied to a calculus expression with some free variables as a function on the attributes of these variables that are referenced in the expression. Doing so, we are able to develop several new processing strategies that should be considered by an optimizer.

Copyright © 1987 by the VLDB Endowment. Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage, the VLDB copyright notice and the title of the publication and its date appear, and notice is given that copying is by the permission of the Very Large Data Base Endowment. To copy otherwise, or to republish, requires a fee and/or special permission from the Endowment.

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Peter M. Stocker, William Kent, Peter Hammersley (Eds.): VLDB'87, Proceedings of 13th International Conference on Very Large Data Bases, September 1-4, 1987, Brighton, England. Morgan Kaufmann 1987, ISBN 0-934613-46-X
Contents

References

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Contents
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