Estimating the number of distinct values for an attribute in a relational database table

摘要

A method and apparatus for estimating the number of distinct values in a database table selects one of several numerical methods to solve a model of the number of distinct values in a database table based on a table size, a sample size, and the number of distinct values in the sample. The sample may be a sample previously collected for purposes other than to estimate the number of distinct values, and the number of records in the sample and the number of distinct values in the sample may be determined at the time the sample was collected.