* Jeremy Zawodny > On Mon, Jan 21, 2002 at 05:18:35PM +0100, Roger Baklund wrote: > > Hi, > > > > Also, I wonder what is the best order for my primary keys: > > > > a int This is the 'main' id, very many distinct values > > b tinyint This is a source code, possible values are 1 or 2 > > c smallint Some counter > > d tinyint Another counter > > > > or > > > > b tinyint This is a source code, possible values are 1 or 2 > > a int This is the 'main' id, very many distinct values > > c smallint Some counter > > d tinyint Another counter > > > > Which will perform faster, when all lookups use both a and b? > > Is this helpful at all?
I don't understand...? Why would it not be? > http://www.linux-mag.com/2001-06/mysql_01.html > > It covers compound indexes (among other topics). I have read this article earlier, and I read the part about compound indexes again now, but I still don't understand why my compound index would not be helpful...? Just to make it clear: this is the primary key, and all four parts of the index are needed to identify the row. Most of the time I use the three first parts, sometimes I use all four parts, and sometimes I use only the first two parts. My question was: is it better to have the part with most distinct values first, or is it better to have the part with very few distinct values first, when _all_ queries _always_ use both parts? I believe the answer to this depends on how the index is stored and handled internally by mysql, and as I do not have this knowledge, I asked the list... I know both ways will work, but as I have rather large amounts of data and speed is important in this application, I would like to do it the optimal way. Thank you for your time. :o) -- Roger --------------------------------------------------------------------- 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
