Set Predicates in SQL: Enabling Set- Level Comparisons for Dynamically Formed Groups

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Name Set Predicates in SQL: Enabling Set- Level Comparisons for Dynamically Formed Groups
Technology Dot net, MS SQL
Category Data Mining
Description In data warehousing and OLAP applications, scalar level predicates in SQL become increasingly inadequate to support a class of operations that require set-level comparison semantics, i.e., comparing a group of tuples with multiple values. Currently, complex SQL queries composed by scalar-level operations are often formed to obtain even very simple set-level semantics. Such queries are not only difficult to write but also challenging for a database engine to optimize, thus can result in costly evaluation. This paper proposes to augment SQL with set predicate, to bring out otherwise obscured set-level semantics. We studied two approaches to processing set predicates—an aggregate function-based approach and a bitmap index-based approach. Moreover, we designed a histogram-based probabilistic method of set predicate selectivity estimation, for optimizing queries with multiple predicates. The experiments verified its accuracy and effectiveness in optimizing queries.
IEEE Paper Yes
IEEE Paper Year 2014
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