:: A sequence is a special kind of database object designed for generating unique numeric identifiers. It is typically used to generate artificial primary keys. Sequences are similar, but not identical, to the AUTO_INCREMENT concept in MySQL. Sequences are most commonly used via the serial pseudotype.[http://neilconway.org/docs/sequences/] - [http://www.postgresql.org/docs/8.1/interactive/datatype.html#DATATYPE-SERIAL]