The present invention provides a uniqueness-required index and a corresponding non-uniqueness count to support deferred uniqueness constraint enforcement. A uniqueness-required index stores duplicate occurrences of indexed data values that occur during statement or transaction processing. The non-uniqueness...http://www.google.se/patents/US6047285?utm_source=gb-gplus-sharePatent US6047285 - Method for using an index as a workspace for deferred enforcement of uniqueness constraints
