RE: Duplicate timestamp(6): How is this possible?

  • From: "Dunbar, Norman (Capgemini)" <norman.dunbar.capgemini@xxxxxxxxxxxxxxxxxxxxxxxxx>
  • To: "Howard Latham" <howard.latham@xxxxxxxxx>
  • Date: Thu, 20 Jan 2011 10:00:23 -0000

Morning Howard,

>> Not that I'm involved in building systems anymore but is 
>> there no longer required to use a sequence to guarantee a 
>> unique id for a record? 
It depends!

You are just about to start the discussion on the merits of natural as
opposed to synthetic keys now. :-)

You would think that a timestamp(6) would be accurate enough to be
unique for all situations - possibly excepting the flow of data from the
LHC at CERN perhaps (16 TB daily apparently), but Oracle's TIMESTAMPS
and TIMESTAMPS WITH TIME ZONEs cause their own problems.

I'd never use a DATE as a primary key, computers work far too fast to
allow second resolution to be unique. (Ok, I admit, as a very junior
COBOL developer on an ICL 2966 mainframe, I did make the mistake of
using a date as a key!)



Cheers,
Norm.

Norman Dunbar
Contract Senior Oracle DBA
Capgemini Database Team (EA)
Internal : 7 28 2051
External : 0113 231 2051


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