I tend to use temporary tables a lot, because I'm doing one-off manipulations where efficiency is not the primary concern and because it helps me think things through. Nonetheless, I've been wondering about this:
SELECT `x` FROM `t1` JOIN (SELECT `x` FROM `t2`) AS `t3` on `t1`.`y` = `t3`.`y`; Table `t3` won't have any indices, even if table `t2` does, is that correct? (Assume that the sub-select is really much more complicated that my example.) Wouldn't it be a lot faster to replace the sub-select with a temporary table that does have a key on `y`? Regards, Jerry Schwartz The Infoshop by Global Information Incorporated 195 Farmington Ave. Farmington, CT 06032 860.674.8796 / FAX: 860.674.8341 <http://www.the-infoshop.com> www.the-infoshop.com <http://www.giiexpress.com> www.giiexpress.com www.etudes-marche.com
