Data processing: database and file management or data structures – Database design – Data structure types
Patent
1997-02-28
1999-11-30
Choules, Jack M.
Data processing: database and file management or data structures
Database design
Data structure types
G06F 1730
Patent
active
059959576
ABSTRACT:
The system, method, and program of this invention collects multi-column statistics, by a database management system, to reflect a relationship among multiple columns of a table in a relational database. These statistics are stored in the system catalog, and are used during query optimization to obtain an estimate of the number of qualifying rows when a query has predicates on multiple columns of a table.
A multi-column linear quantile statistic is collected by dividing the data of multiple columns into sub-ranges where each sub-range has approximately an even distribution of data, and determining a frequency and cardinality of each sub-range. A multi-column polygonal quantile statistic is collected by dividing the data of multiple columns into sub-spaces where each sub-space contains approximately the same number of tuples, and determining a frequency and cardinality of each sub-space.
The system catalog is accessed for the stored multi-column linear quantile statistic for a query having a single range predicate and at least one equal predicate to determine the selectivity value for the predicates of the query. The system catalog is accessed for the stored multi-column polygonal quantile statistic for a query having more than one range predicate. These statistics are used in various ways to determine the selectivity value for the predicates of the query.
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Gassner, P. et al., "Query Optimization in the IBM DB2 Family," Bulletin of the Technical Committee on Data Engineering, IEEE Computer Society, Dec. 1993, vol. 16, No. 4, pp. 4-18.
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Beavin Thomas Abel
Iyer Balakrishna Raghavendra
Shibamiya Akira
Tie Hong Sang
Wang Min
Choules Jack M.
International Business Machines - Corporation
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