1. A system for searching through multiple databases based on a search expression, said system comprising: means for defining distribution of records corresponding to search keys in said databases; means for dividing said search expression into multiple search expressions based in part on the defined distribution of records, and determining respective, target search ranges for said multiple search expressions such that a number of records to be searched with each of said multiple search expressions is approximately constant; and means for executing said multiple search expressions in their respective, target search ranges.