A method for estimating the result of a query on a database having data records arranged in tables. The database has an expected workload that includes a set of queries that can be executed on the database. A sample is constructed by selecting data records for inclusion in the sample in a manner that minimizes an estimation error when the data records are acted upon by a query in the expected workload to provide an estimated result. The query accesses the sample and is executed on the sample, returning an estimated query result. The expected workload can be constructed by specifying a degree of overlap between records selected by queries in the given workload and records selected by queries in the expected workload.