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  3. July 2012

Re: Indexed PF vs. LF performance

I would agree. I define all new tables in SQL with primary keys based
on identity keys so no way to get around it. We did foreign keys on
all our new driver manager tables but lots of issues.

On Mon, Jul 30, 2012 at 3:56 PM, DeLong, Eric <EDeLong@xxxxxxxxxxxxxxx> wrote:
Really? I thought that rule went out eons ago...

FWIW, I try to define PRIMARY KEY on all my SQL defined files. I'm not sure if you can define foreign key constraints without primary key, so as far as I can tell, optimal DB design would always prefer to have a unique single field primary key. Compound primary keys work too, but I suspect this would be considered less than ideal... But, since nobody ever defines foreign key relationships within DB2/i, then this is probably a moot point.

Eric

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Bradley Stone
Sent: Monday, July 30, 2012 3:43 PM
To: Midrange Systems Technical Discussion
Subject: Re: Indexed PF vs. LF performance

I'd also say they are probably the same or close enough to not make it
an issue.

But I also like to follow the rule of never keying a PF. :) But
that's just me.

Brad
www.bvstools.com

On Mon, Jul 30, 2012 at 3:41 PM, John Yeung <gallium.arsenide@xxxxxxxxx> wrote:
On Mon, Jul 30, 2012 at 4:19 PM, Tim Adair <tadair@xxxxxxxxxxxxxxxx> wrote:
A colleague asked me about this and I haven't been able to find any
definitive information.

Thoughts please?

My guess is that they are about the same, for the scenario you describe.

However, the only way to have *truly* definitive information *for your
specific situation* is to try both. (This is one of the fundamental
guiding principles of optimization: measure, don't guess.)

John
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