Laws for Rewriting Queries Containing Division Operators

Rantzau, Ralf; Mangold, Christoph

doi:10.1109/icde.2006.180

Cited by 8 publications

(5 citation statements)

References 28 publications

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“…It is unlikely that this approach can be extended to the distributed case -although it could be used to process quantifiers in the node responsible for the query. There has also been much work on efficiently supporting universal quantification in SQL in centralised settings; see Rantzau and Mangold [33] for a recent sample. The language QLðQÞ and its implementation were studied in depth in [4]; we have reused here the language definition and the basic (centralised) processing techniques.…”

Section: Related Workmentioning

confidence: 99%

Supporting quantified queries in distributed databases

Badia

Dobbs

2014

International Journal of Parallel, Emergent and Distributed Sys

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We show that some relational queries, which we call quantified queries are not well supported in distributed environments. We give a formal definition of quantified queries, propose a language in which to express said queries and provide a procedure to compute answers in this new language in the context of distributed databases. The proposed language is made up of high-level, declarative operators (called generalised quantifiers), and therefore it can be used in combination with several distributed frameworks. Our approach is designed to be as general as possible; it assumes horizontally partitioned relations, but nothing else, so no data placement or replication is used. We present an implementation and algorithms for the new language, propose some basic optimisations and give experimental results which show that the new approach is indeed quite efficient and scales well.

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Section: Related Workmentioning

confidence: 99%

Supporting quantified queries in distributed databases

Badia

Dobbs

2014

International Journal of Parallel, Emergent and Distributed Sys

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“…They implement their approach using a new operator called the Multidimensional join operator. While [26] focuses on universal quantification and gives several optimization choices based on RA, for us universal quantification is but one case among many (although admittedly an important case). Note that we provide several options for computing universal quantification, and leave it up to the optimizer to decide which one to use for a given query.…”

Section: Related Researchmentioning

confidence: 99%

“…A well studied example is that of universal quantification ( [12,26]). SQL relies on paraphrases that make formulas complex for users and difficult for the optimizer too, since it has to work harder to process them in an efficient manner.…”

Section: Motivationmentioning

confidence: 99%

“…It is likely a combination of such factors that has led to the lack of a universal quantifier in Relational Algebra (henceforth RA) and SQL: it is easy to see that certain queries with universal quantification, in interaction with other features, can led to high complexity ( [12,26]). However, there is no lack of expressive power in such languages: universal quantification can be expressed through negation (relative negation, or set difference, for safety reasons) and existential quantification.…”

Section: Introductionmentioning

confidence: 99%

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Efficient implementation of generalized quantification in relational query languages

Badia

Cao

2013

Proc. VLDB Endow.

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We present research aimed at improving our understanding of the use and implementation of quantification in relational query languages in general and SQL in particular. In order to make our results as general as possible, we use the framework of Generalized Quantification. Generalized Quantifiers (GQs) are high-level, declarative logical operators that in the past have been studied from a theoretical perspective. In this paper we focus on their practical use, showing how to incorporate a dynamic set of GQs in relational query languages, how to implement them efficiently and use them in the context of SQL. We present experimental evidence of the performance of the approach, showing that it improves over traditional (relational) approaches.

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“…In each world we find the destinations, and then close the possible worlds semantics by computing the certain destinations. Assuming the existence of a division operator in SQL [22], we can express the query in SQL as (assuming set-based semantics for SQL and I-SQL): This computes all arrival cities that appear in combination with all departures. Division can be simulated in SQL using a nested subquery with two not-exists constructs: This shows that at least in certain cases, I-SQL allows to phrase decision support queries more concisely than plain SQL.…”

Section: Application Scenariosmentioning

confidence: 99%

From complete to incomplete information and back

Antova

Olteanu

2007

Proceedings of the 2007 ACM SIGMOD International Conference on Management of Data

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Incomplete information arises naturally in numerous data management applications. Recently, several researchers have studied query processing in the context of incomplete information. Most work has combined the syntax of a traditional query language like relational algebra with a nonstandard semantics such as certain or ranked possible answers. There are now also languages with special features to deal with uncertainty. However, to the standards of the data management community, to date no language proposal has been made that can be considered a natural analog to SQL or relational algebra for the case of incomplete information.In this paper we propose such a language, World-set Algebra, which satisfies the robustness criteria and analogies to relational algebra that we expect. The language supports the contemplation on alternatives and can thus map from a complete database to an incomplete one comprising several possible worlds. We show that World-set Algebra is conservative over relational algebra in the sense that any query that maps from a complete database to a complete database (a complete-to-complete query) is equivalent to a relational algebra query. Moreover, we give an efficient algorithm for effecting this translation. We then study algebraic query optimization of such queries.We argue that query languages with explicit constructs for handling uncertainty allow for the more natural and simple expression of many real-world decision support queries. The results of this paper not only suggest a language for specifying queries in this way, but also allow for their efficient evaluation in any relational database management system.

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Laws for Rewriting Queries Containing Division Operators

Abstract: Abstract

Cited by 8 publications

References 28 publications

Supporting quantified queries in distributed databases

Supporting quantified queries in distributed databases

Efficient implementation of generalized quantification in relational query languages

From complete to incomplete information and back

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