The UUID() function returns a Universally Unique Identifier (UUID).
A UUID is designed as a spatially and temporally unique number worldwide. Two calls to UUID() result in two different values, even if those calls are made on two different servers.
A UUID is a 128-bit number represented by a string of five hexadecimal digits in the format aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee:
The first three numbers are generated from a timestamp.
The fourth number preserves the temporal uniqueness in case the timestamp value loses continuity, for example due to daylight saving time.
The fifth number is an IEEE 802 node number, for spatial uniqueness. If a node number is not available, it is replaced with a random number. In this case, spatial uniqueness cannot be guaranteed.