   UUID()

Returns a Universal Unique Identifier (UUID) generated
according to ``DCE 1.1: Remote Procedure Call'' (Appendix A)
CAE (Common Applications Environment) Specifications
published by The Open Group in October 1997 (Document Number C706).

A UUID is designed as a number that is globally unique in space and
time. Two calls to UUID() are expected to generate two different
values, even if these calls are performed on two separate computers that are
not connected to each other.

A UUID is a 128-bit number represented by a string
of five hexadecimal numbers in aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee
format:


 --- The first three numbers are generated from a timestamp.

 --- The fourth number preserves temporal uniqueness in case the timestamp value loses
monotonicity (for example, due to daylight saving time).

 --- The fifth number is an IEEE 802 node number that provides spatial uniqueness.  A
random number is substituted if the latter is not available (for example,
because the host computer has no Ethernet card, or we do not know how to
find the hardware address of an interface on your operating system).  In
this case, spatial uniqueness cannot be guaranteed. Nevertheless, a
collision should have /very/ low probability.

Currently, the MAC address of an interface is taken into account only on
FreeBSD and Linux. On other operating systems, MySQL uses a randomly generated
48-bit number.
