Just to let you know, the substring() was slightly slower.
From: T L <tloud365@gmail.com>
To: development@drupal.org
Sent: Mon, July 19, 2010 10:20:26 PM
Subject: Re: [development] MySql Performance Problem
What about substring() instead of concat() or adding a column for the nid in ppc and pmc?
Cheers,
tim