uuid

UUID - Universally unique id is a 128 bit is a reasonably unique value. UUID was standarized by Open Software Foundation and Distributed Computing Environment. Purpose of UUID is to generate a universally unique identifier without contacting a central identifier generation system.

UUID are relavant to distributed computing, each machine can have 10 million UUID per second as per IETF REFC 4122 . Implementation for generating UUID are widely available in various programming language libraries and in DBMS.

JDK 1.5 provides classes to generate UUID.

Oracle SYS_GUID() , MySQL UUID() , SQL Server NEWID()