SQL Server 如何使用 NEWID() 创建唯一标识符 [英] How SQL Server creates uniqueidentifier using NEWID()
问题描述
我在五个不同的位置有一个 user_info
表.现在我需要将所有行集成到一个中央 user_info
表中.为此,我需要源表中每一行的唯一 ID.因为当所有的行都进入中央表时,那么每个用户都必须有一个唯一的 ID.
I have a user_info
table in five different locations. Now I need to integrate all the rows into a central user_info
table. To do this I need a unique id for each row in source tables. Because when all the rows come into the central table, then each user must have a unique ID.
现在我的问题是:
如果我对每个源表使用
uniqueidentifier
NEWID()
那么它对于全局来说是唯一的吗?生命的时间还是有机会被复制?
if I use
uniqueidentifier
NEWID()
for each source table then is it will be unique for globally & life time or have any chance to be duplicate?
SQL Server 如何创建NEWID()
?我需要知道密钥生成结构.
How does SQL Server create the NEWID()
? I need to know the key generation structure.
推荐答案
是的,机器之间不可能有重复.
Yes, there is no chance of a duplicate between machines.
NEWID()
基于伪随机数(来自时钟)和主 NIC 的 MAC 地址的组合.
NEWID()
is based on a combination of a pseudo random number (from the clock) and the MAC address of the primary NIC.
然而,像这样插入随机数作为表上的聚集键对性能来说是很糟糕的.您应该考虑使用 NEWSEQUENTIALID()
或 COMB 类型的函数来生成 GUID,这些函数仍提供 NEWID()
的冲突避免优势,同时仍保持可接受的 INSERT
性能.
However, inserting random numbers like this as the clustered key on a table is terrible for performance. You should consider either NEWSEQUENTIALID()
or a COMB-type function for generating GUIDs that still offer the collision-avoidance benefits of NEWID()
while still maintaining acceptable INSERT
performance.
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