1. A method that samples with replacement a plurality of records in a database system in a single sequential pass of the records, comprising: identifying the plurality of records; determining a sum of weights to be assigned to all records in the plurality of records; when a record is selected to be included in the sample, tabulating a remaining weight that subtracts all weights associated with records included in the sample from the sum of weights; for each of the plurality of records: inputting the record to a sampling operator that determines a number of times the record is included in the sample by generating a random value from a binomial distribution using the remaining weight and a weight of the current record as parameters; and selectively outputting and storing the record for inclusion in the sample the determined number of times, wherein the record may be included more than one time in the sample.