首页>
外国专利>
Evaluation of grouping sets by reduction to group-by clause, with or without a rollup operator, using temporary tables
Evaluation of grouping sets by reduction to group-by clause, with or without a rollup operator, using temporary tables
展开▼
机译:使用临时表,通过归纳为group-by子句来评估分组集,无论是否使用汇总运算符
展开▼
页面导航
摘要
著录项
相似文献
摘要
Methods are provided for efficiently evaluating database queries that include a grouping sets specification, by reducing the grouping sets specification to one or more combinations of groupings that are computable with simple GROUP BY clauses, with or without a rollup operator, wherein the GROUP BY clauses and rollup operators are efficient operations that can be computed with a single data sort. Computational costs are further minimized by computing a grouping from records generated from computation of a previously computed grouping. An optimization algorithm is described which determines the respective grouping combinations to which the grouping sets specification is reduced and the respective GROUP BY clauses, to minimize computational costs. Furthermore, an intermediate grouping, that is, a grouping that is not specified by the query, is included in a query evaluation plan in some instances, to compute specified groupings when doing so reduces computational costs.
展开▼