在Jimmy Nilsson The Cost of GUIDS as Primary Keys里对GUID的生成做了详细的说明:
“The algorithm for generating GUIDs doesn’t use the MAC address of the network card in recent Windows versions anymore.Instead ,it just creates a random value.In theory,this presents a risk of getting duplicate GUIDs,but,in practice,it shouldn’t be a problem”
“The reason for excluding the use of the MAC address is that it not only couples users to GUIDs,but some network cards don’t use unique MAC address.”
对于这个情况,Jimmy Nilsson还分别在nt 4+sql 7 和 windows 2000+ sql 2000上做了实验,实验证明确实如此,在GUID的16位随机数当中,有15.5位是随机的,怎么出来个15.5?是这样的,如果你按照半个字节来数的话,第13位,也就是第
