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Message Posted: Thu, 22 May 2003 @ 15:20:37 GMT

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Subj:   Re: Time Stamp in Teradata
From:   Geoffrey Rommel

  So if you select without ORDER BY you'll always end upwith an unordered result set. This is different to mostother RDBMSes.  

I hesitate to disagree with Dieter, but this is not quite correct. In relational theory, relations are sets, so they are unordered. For instance, the set {integers between 1 and 20} can be enumerated in a conventional order -- 1, 2, 3, etc. -- but there is no order to the set itself; all 20! enumerations specify the same set. In other RDBMSes, the rows may in fact come out in the same order every time, but this is merely a by-product of the physical ordering on disk; it does not imply that there is an order to the rows of the table.

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