RE: 'Theoretical' SQL question

["Walden H. Leverich" <WaldenL@xxxxxxxxxxxxxxx>]

>Which was can one assume _100%_ that the processing 
>will stop once the record has been located. 

Philip,

I think you miss the point though, you cannot assume _anything_ that is
not explicitly stated in your select (update, delete, whatever)
statement. For example, say your table had 10 rows in it, not 10
Million, just 10. Even with an index on item number, the system may
decide it's faster to just read the table, after all, I'm sure it would
come in in a single read.

Also, you make an assumption that the processing is sequential -- on a
multiprocessor, or even SMT machine, the system may split up the query
and multiple parts at the same time, define "stop" in that case.

Even if you could predict what the system would do, it could change from
PTF to PTF as newer better techniques are developed. 

Finally, why do you care? Seriously, if the data returned is what you
asked for, who cares _how_ it does it, as long as it does it fast? 

-Walden


------------
Walden H Leverich III
President & CEO
Tech Software
(516) 627-3800 x11
WaldenL@xxxxxxxxxxxxxxx
http://www.TechSoftInc.com

Quiquid latine dictum sit altum viditur.
(Whatever is said in Latin seems profound.)


-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Hall, Philip
Sent: Thursday, January 20, 2005 8:38 PM
To: Midrange Systems Technical Discussion
Subject: RE: 'Theoretical' SQL question

> If the field is a unique key, it got to be an index.
> If it is an index, then table scan is not needed - so there is no
issue.
> 
> Do I miss something here?
> 

Yes, my original question.

Which was can one assume _100%_ that the processing will stop once the
record has been located.


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