Data Base Parameters: Equijoin and Semijoin
نویسنده
چکیده
summary by Dani ele Gardy]
منابع مشابه
Investigating the 2-way Semijoin for Distributed Query Optimization
With increased globalization, most databases are now highly distributed. Thus, there is a need to reduce the cost of queries that require data from several locations. In the literature, the semijoin is the most commonly used operation for the reduction phase of any distributed query optimization strategy. In [7] an improvement, called the 2-way semijoin, is proposed. The authors conclude that t...
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In this paper we consider processing entity join queries in a wide area multidatabase environmen t where the query processing cost is dominated by the cost of data transmission An entity join oper ation integrates tuples representing the same en tities from di erent relations in which inconsistent data may exist The semijoin technique has been successfully used in a distributed database system ...
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The semijoin algebra is the variant of the relational algebra obtained by replacing the join operator by the semijoin operator. We provide an Ehrenfeucht-Fraissé game, characterizing the discerning power of the semijoin algebra. This game gives a method for showing that queries are not expressible in the semijoin algebra.
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ÐIn a distributed spatial database system, a user may issue a query that relates two spatial relations not stored at the same site. Because of the sheer volume and complexity of spatial data, spatial joins between two spatial relations at different sites are expensive in terms of computation and transmission cost. In this paper, we address the problems of processing spatial joins in a distribut...
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This paper presents a new data structure for multiway and general join query acceleration, the hit-list, and an algorithm for its use. The hit-list is a surrogate index providing the mapping between the values of two attributes in a relation participating in an equijoin or a selection. The results of an analytical model, simulation study, and an implementation are presented. The performance adv...
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