"Craig Manley" <bitneuker666(at)hotmail(dot)com> writes:
> Some databases have a hidden field that contains a row version key.
> Everytime an update is performed on a row the value of the version field
> changes. Does PostgreSQL have a similar hidden field?
See xmin (and also cmin if you need to keep track of multiple changes
intra-transaction). It might not be defined quite the way you want,
but if you're not picky about what a "version number" is, it'll do.
regards, tom lane