At 21:30 -0800 2/10/02, Jeremy Zawodny wrote: >On Sun, Feb 10, 2002 at 10:01:45PM -0600, Paul DuBois wrote: >> At 18:07 -0800 2/10/02, Jeremy Zawodny wrote: >> >On Sun, Feb 10, 2002 at 02:53:53PM -0500, Matthew Dougherty wrote: >> >> If I use a REGEXP query on an indexed column using something like: >> >> Field REGEXP '^A|^B|^C' >> >> >> >> Will MySQL use the index like it would if I used Field LIKE 'A%' or >> >> Field LIKE 'B%' or FIeld LIKE 'C%' ?? >> > >> >It will not. >> > >> >Regular expressions are best used when you need something more complex >> >than what "%" allows you to achieve. >> >> Not to mention that an index won't be used even for the LIKE expression, >> because it uses OR. At least, I think it won't be. > >Hm. It looks like it will in 4.0.2, at least:
Cool! > >mysql> describe S2H; >+------------+-------------+------+-----+---------+-------+ >| Field | Type | Null | Key | Default | Extra | >+------------+-------------+------+-----+---------+-------+ >| Symbol | varchar(75) | | PRI | | | >| HeadlineId | int(11) | | PRI | 0 | | >+------------+-------------+------+-----+---------+-------+ >2 rows in set (0.06 sec) > >mysql> explain select * from S2H where Symbol like "y%" or Symbol like >mysql> "c%"; >+-------+-------+---------------+--------+---------+------+--------+------------+ >| table | type | possible_keys | key | key_len | ref | rows | >mysql> Extra | >+-------+-------+---------------+--------+---------+------+--------+------------+ >| S2H | range | Symbol | Symbol | 75 | NULL | 129617 | >where used | >+-------+-------+---------------+--------+---------+------+--------+------------+ >1 row in set (0.06 sec) > >Jeremy >-- >Jeremy D. Zawodny, <[EMAIL PROTECTED]> >Technical Yahoo - Yahoo Finance >Desk: (408) 349-7878 Fax: (408) 349-5454 Cell: (408) 685-5936 > >MySQL 3.23.47-max: up 3 days, processed 128,435,474 queries (409/sec. avg) > >--------------------------------------------------------------------- >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 --------------------------------------------------------------------- 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
