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Posted by David Portas on 10/16/07 21:20
On 16 Oct, 13:32, Tim <tim_roger...@hotmail.com> wrote:
> Hi Folks,
>
> I come from an Informix background, (pauses for the laughter to die
> down), where SQL can access a hidden attribute, (ROWID), that uniquely
> identifies each record in a table at that point in time. It's similar
> to an IDENTITY attribute but it is not visible unless specifically
> selected and the RDBMS actively re-uses the numbers as they become
> vacant through deletion of records.
>
> However it can be very useful if you are trying to unscramble static
> but erroneously duplicate data rows built up due to an 'undocumented
> feature' of the application software. This is the situation I find
> myself in at the moment, so I was wondering if there was anything of a
> similar nature hidden or undocumented in SQL Server?
>
> I realise I could make a copy of the table and add an IDENTITY
> attribute, but I'm playing with some 75,000,000 rows of data that must
> all be salvaged, which complicates matters a little.
>
> Tia, Tim
Depending on requirements there are a few ways you can de-duplicate
data. Google in microsoft.public.sqlserver.programming.
Despite what you say, it seems that an "undocumented feature" of your
application was not the cause of the problem. The cause was that you
have a table without a key. Adding a key constraint should be your
priority. IDENTITY won't help because it won't stop your application
inserting duplicate data.
--
David Portas
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