| 摘要 |
A method, system, and/or computer program product estimate a cardinality of a joined table (T) obtained by joining at least a first data column (R) and a second data column (S), where R and S each comprise attribute values. A first density distribution function f(x) describes a frequency of the attribute values of R. A second density distribution function (g(x)) describes the frequency of the attribute values of S. A first information on values in R is based on a sample of values of R. A second information on values in S is based on a sample of values of S. One or more processors then estimate a cardinality of a joined table (T) based on the first and second density distribution function (f(x), g(x)) and the first and second information on values. |
