RE: select distinct values

From: Robson, Peter <pgro_at_bgs.ac.uk>
Date: Thu, 25 Sep 2003 01:44:40 -0800
Message-ID: <F001.005D0F85.20030925014440@fatcity.com>

Whoa there!

See below:

> -----Original Message-----
> From: elain he [mailto:elainhe_at_hotmail.com]
> Sent: Tuesday, September 23, 2003 9:40 PM
> To: Multiple recipients of list ORACLE-L
> Subject: select distinct values
>
>
> Hi,
> Could someone shed some light on this.
>
> I'm trying to formulate a query to return distinct value on a
> column -
> testid.
>
> select * from testing;
> TESTID NAME STATUS
> ---------- -------------------- -----------
> 1 MIKE Y
> 1 JOE Y
> 1 JIM Y
> 2 AMY Y
>
> The output I'm expecting is
> TESTID NAME STATUS
> ---------- -------------------- -----------
> 1 MIKE Y
> 2 AMY Y
>

---

This sentance contains a fundamental error of understanding of a relational db.
>
> The query should display the first occurence of the testid and ignore
> records with the same testid.
>

The ORDER in which rows are retrieved from a table is not, never, ever will be significant. By definition.

So if you can find a script which appears to give you the correct result for this example, then sure as eggs is eggs, it will fail on another data set. There is NOTHING in your example data set which enables a logical predicate to establish precedence of any one row with Testid=1 over another.

peter
edinburgh

---

> thanks!
>
> elain
>
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---

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-- 
Author: Robson, Peter
  INET: pgro_at_bgs.ac.uk

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Received on Thu Sep 25 2003 - 04:44:40 CDT