Benjamin Pflugmann wrote: > If you have 256MB, the one may fit into memory, > the other may not and therefore requires additional disk reads.
Ah, see.. I hadn't thought of disk reads. I was thinking if you do a select on a char[50] and the whole field is indexed, wouldn't the search algorithm know exactly where to go to look for a match, as opposed to - if only the first 20 characters are indexed - finding all of the possible values that match the first 20 and then having to go through all of them looking for a match? It would seem like, from what I know of indexes, if the whole field is indexed, only one disk read should be necessary since it would go right to that row the first time. But I admittedly have never peeked inside the mySQL source code, so maybe it doesn't work that way...again not arguing, just looking for insight. Thanks, T SQL MySQL --------------------------------------------------------------------- Before posting, please check: http://www.mysql.com/manual.php (the manual) http://lists.mysql.com/ (the list archive) To request this thread, e-mail <[EMAIL PROTECTED]> To unsubscribe, e-mail <[EMAIL PROTECTED]> Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php
