Outerjoin optimization in multidatabase systems

Outerjoin is used in distributed relational multidatabase systems for integrating local schemas to a global schema. Queries against the global schema need to be modified, optimized, and decomposed into subqueries at local sites for processing. Since outerjoin combines local relations in different da...

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Bibliographic Details
Published inDatabases in Parallel and Distributed Systems: 2nd International Symposium pp. 211 - 218
Main Author Chen, A.L.P.
Format Conference Proceeding
LanguageEnglish
Published IEEE Comput. Soc. Press 1990
Subjects
Delay
Distributed databases
Environmental management
Null value
Parallel processing
Query processing
Relational databases
Resource management
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ISBN9780818620522
0818620528
DOI10.1109/DPDS.1990.113712

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Summary:Outerjoin is used in distributed relational multidatabase systems for integrating local schemas to a global schema. Queries against the global schema need to be modified, optimized, and decomposed into subqueries at local sites for processing. Since outerjoin combines local relations in different databases to form a global relation, it is expensive to process. Based on the structure of the query and the definition of the schemas, queries with outerjoin, join, select and project operations are optimized. Conditions where outerjoin can be avoided or transformed into a one-sided outerjoin are identified. Considering these conditions makes it possible to reduce the response time for query processing.< >
ISBN:9780818620522
0818620528
DOI:10.1109/DPDS.1990.113712