Results 191 to 200 of about 327,421 (217)
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2020
When you submit a query to MySQL for execution, it is not as simple as just reading the data and returning it. True, for simple queries requesting all data from a single table, there are not many options how to retrieve the data. However, most queries are more complex – some much more complex – and executing the query exactly as it is written is by no ...
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When you submit a query to MySQL for execution, it is not as simple as just reading the data and returning it. True, for simple queries requesting all data from a single table, there are not many options how to retrieve the data. However, most queries are more complex – some much more complex – and executing the query exactly as it is written is by no ...
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Query Processing and Optimization
2000The ultimate purpose of a data warehouse is to support queries by end users who want to analyze the available information for an organization. However, from a more abstract point of view, queries are not only processed at the data warehouse back end.
Panos Vassiliadis +3 more
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Optimizing query rewriting for multiple queries
Proceedings of the Ninth International Workshop on Information Integration on the Web, 2012We present an scalable algorithm for answering multiple conjunctive queries using views. This is an important problem in query optimization, data integration and ontology-based data access. Since rewriting one conjunctive query using views is an NP-hard problem, we develop an approach where answering n queries takes less than n times the cost of ...
George Konstantinidis, José Luis Ambite
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ACM SIGMOD Record, 1986
In some recently proposed extensions to relational database systems as well as in deductive databases, a database system is presented with a collection of queries to process instead of just one. It is an interesting problem then, to come up with algorithms that process these queries together instead of one query at a time.
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In some recently proposed extensions to relational database systems as well as in deductive databases, a database system is presented with a collection of queries to process instead of just one. It is an interesting problem then, to come up with algorithms that process these queries together instead of one query at a time.
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Optimization and evaluation of disjunctive queries
IEEE Transactions on Knowledge and Data Engineering, 2000It is striking that the optimization of disjunctive queries-i.e. those which contain at least one OR-connective in the query predicate-has been vastly neglected in the literature, as well as in commercial systems. In this paper, we propose a novel technique, called bypass processing, for evaluating such disjunctive queries.
Claussen, Jens +4 more
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Progressive Query Optimization for Federated Queries
2006Database Management Systems (DBMS) perform query plan selection by mathematically modeling the execution cost of candidate execution plans and choosing the cheapest query execution plan (QEP) according to that cost model. The cost model requires accurate estimates of the sizes of intermediate results of all steps in the QEP.
Vijayshankar Raman +3 more
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Distributed Query Optimization by Query Trading
2004Large-scale distributed environments, where each node is completely autonomous and offers services to its peers through external communication, pose significant challenges to query processing and optimization. Autonomy is the main source of the problem, as it results in lack of knowledge about any particular node with respect to the information it can ...
Fragkiskos Pentaris, Yannis Ioannidis
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Optimizing a Query by Transformation and Expansion
2017In the biomedical sector not only the amount of information produced and uploaded into the web is enormous, but also the number of sources where these data can be found. Clinicians and researchers spend huge amounts of time on trying to access this information and to filter the most important answers to a given question.
Alexander Knurr +8 more
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Proceedings of 16th International Conference on Data Engineering (Cat. No.00CB37073), 2002
We demonstrate a Web Query Optimizer (WQO) within an architecture of mediators and wrappers, for WebSources of limited capability in a wide area environment. The WQO has several innovative features, including a CBR (capability based rewriting) tool, an enhanced randomized relational optimizer extended to a Web environment, and a WebWrapper cost model ...
Louiqa Raschid +4 more
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We demonstrate a Web Query Optimizer (WQO) within an architecture of mediators and wrappers, for WebSources of limited capability in a wide area environment. The WQO has several innovative features, including a CBR (capability based rewriting) tool, an enhanced randomized relational optimizer extended to a Web environment, and a WebWrapper cost model ...
Louiqa Raschid +4 more
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Semantic query optimization for object queries
1995Semantic query optimization is an approach to query optimization that utilizes semantic knowledge to reformulate a query into one that would generate the same set of answers in a more efficient way. The semantic query optimization becomes more important in OODB systems where object queries are complex due to the presence of object-oriented concepts ...
Young-Whun Lee, Suk I. Yoo
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