Hi Rob.
Thank you very much for your answer.
CREATE TABLE `books` (
`id` int(11) unsigned NOT NULL auto_increment,
`title` varchar(200) NOT NULL,
`author_name` varchar(100) NOT NULL,
`category_name` varchar(100) NOT NULL,
`description` varchar(200) NOT NULL,
`isbn` varchar(100) NOT NULL,
PRIMARY KEY (`isbn`),
KEY `id` (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=227976 DEFAULT CHARSET=utf8
AUTO_INCREMENT=227976 ;
-------------------------------------------------
EXPLAIN SELECT * FROM books WHERE isbn='978-0-19-280239-2' LIMIT 1
id=1
select_type=SIMPLE
table=books
type=const
possible_keys=PRIMARY
key=PRIMARY
key_len=302
ref=const
rows=1
Extra=
----------------------
Regards,
--Charles
On 4/27/08, Rob Wultsch <[EMAIL PROTECTED]> wrote:
>
> On Sun, Apr 27, 2008 at 3:59 AM, Charles Lambach
> <[EMAIL PROTECTED]> wrote:
> > I do _always_ this query:
> > SELECT * FROM books WHERE isbn='foo' LIMIT 1
> >
> > The primary key of this table was 'id', and 'isbn' was and INDEX field.
>
>
> This sentence could have been better written. If you have a primary
> key index on (id,isbn) and isbn is not indexed as the left most column
> of another index then an index would not be used for the above query.
> If you have a prymary key index on (id) and another index on ('isbn')
> then that index would probably be used.
>
> It would much easier to tell you whats going on if you post your DDL
> (so post the output of 'SHOW CREATE TABLE books;') and your EXPLAIN
> (so post the output of 'EXPLAIN SELECT * FROM books WHERE isbn='foo'
> LIMIT 1;').
>
>
> --
> Rob Wultsch
> [EMAIL PROTECTED]
> wultsch (aim)
>
