Patent ID: 6272487
Filing Date: 2001-08-07
Classification: G06F,Y10S

Abstract:
A method for use in a database management system for optimizing a query, the method comprising:collecting at least one type of multi-column statistic to reflect a relationship among multiple selected non-indexed columns of a table, wherein the step of collecting at least one type of multi-column statistic further comprises collecting a first type of multi-column quantile statistics for indicating a number of rows between two given values by dividing the data into a plurality of sub-ranges, each sub-range having an even distribution of data, and determining a frequency and cardinality of each sub-range; andstoring the at least one type of multi-column statistic in a table for subsequent use in determining a selectivity value (a number of qualified rows) for predicates in the query, wherein the selectivity value is used in optimizing execution of the query.