Re: What is a ROW-ID
From: Tibor Karaszi (tibor_please.no.email_karaszi_at_hotmail.nomail.com)
Date: 03/23/04
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Date: Tue, 23 Mar 2004 09:28:51 +0100
Just to (hopefully) emphasize David's point a bit:
When Edgar Codd wrote down the 12 fundamental rules for a relational
database system, one of the most fundamental is that the DBMS should not
expose internal/physical attributes of the data. This is what David refers
to as "Physical Data Independence".
Since this is a very basic concept, most decent books about relational
database systems should include comments on this, if you want to dig into
the "why" topic. Also, I'm sure that there are plenty of info on the net.
Note that the "theoretic" aspects of relational systems isn't debated as
much today as one, two or three decades ago, so more elaborate information
is often found in older books or more fundamental books.
Here's a link to some real fundamental stuff:
http://palslib.com/Fundamentals/The_Relational_Model.html
-- Tibor Karaszi, SQL Server MVP http://www.karaszi.com/sqlserver/default.asp "Abhishek Srivastava" <abhishek-srivastava@nospam.net> wrote in message news:%233gjBiKEEHA.700@TK2MSFTNGP09.phx.gbl... > Thanks for the clarification. In a general sense every database has the > concept of an identity key (oracle calls it sequence) However, why do > they have this, why not use the row id itself. [I learnt from a friend > that almost all databases have concept of Row ID.] > > Do all databases hide the Row ID from the user? Is there a reason for > hiding the Row ID from the user? > > Thanks for your help and patience. > > regards, > Abhishek. > > David Portas wrote: > > > SQL Server doesn't expose physical row identifiers to the user so there is > > no "Row ID" in SQL Server. The IDENTITY property is a method of creating a > > system-generated surrogate key. > >
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