UUID

mysql uuid() arba PHP https://gist.github.com/dahnielson/508447/b271e314c3c3190b0e31bc7f2f4f35da3c04f91c

Version 1 (date-time and MAC address)
Version 2 (date-time and MAC Address, DCE security version)
Versions 3 and 5 (namespace name-based)
Version 4 (random)