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, <jzawodn@stripped>
>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)
>
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