A database server supports weighted and unweighted sampling of records or tuples in accordance with desired sampling semantics such as with replacement (WR), without replacement (WoR), or independent coin flips (CF) semantics, for example. The database server may perform such sampling sequentially not...http://www.google.es/patents/US7567949?utm_source=gb-gplus-sharePatente US7567949 - Sampling for database systems
