Re: Optimizing table (shall I create a primary field?)

[Rob Wultsch]

On Sun, Apr 27, 2008 at 3:59 AM, Charles Lambach
<charles.lambach@stripped> 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
wultsch@stripped
wultsch (aim)