Re: Re: the opposite of a join?
| From: | Chris | Date: | Thu, 04 Oct 2007 01:56:18 +0000 |
| Subject: | Re: Re: the opposite of a join? | ||
| References: | 1 2 3 4 5 6 7 | Groups: | php.db php.general |
| Request: | Send a blank email to php-general+get-262723@lists.php.net to get a copy of this message | ||
Robert Cummings wrote:
On Thu, 2007-10-04 at 11:23 +1000, Chris wrote:A subselect could win out in terms of performance especially if the table in the subselect is reasonably small (eg all fits into memory). -- Postgresql & php tutorials http://www.designmagick.com/Robert Cummings wrote:Yes, but you're not going to get a performance improvement if you use anything else if the table isn't properly indexed.On Wed, 2007-10-03 at 14:49 -0700, Jim Lucas wrote:If indexed properly of course ;)This is only from my own personal testing. Mind you that I have only been using PostgreSQL for a year or so. But one problem that I have always ran into with MySQL is that when JOIN'ing tables that have large data sets is a PITA.Were you doing left joins when you experienced those problems? Left joins are usually very fast.