On Tuesday 18 March 2003 02:47, dreq jkj wrote:
I have trouble figuring out how the indices are used when making a query
that uses OR-operator.
If I have the following table:
create table testing(
id int unsigned not null primary key auto_increment,
idx1 int unsigned not null,
idx2 int unsigned not null,
index(idx1),
index(idx2));
In this query i expect mySQL to use one of the two indices to speed up the
query, but It doesn't.. :(
select * from testing where idx1=0 or idx2=1;
Yes, MySQL doesn't use indexes in this way:
http://www.mysql.com/doc/en/Searching_on_two_keys.html
The thing I'm thinking about instead is the following query:
select * from testing where idx1=0
UNION
select * from testing where idx2=1;
It looks like this does speed up the query, but is this the way to go???
Is this a weaknes in mySQL or have I forgotten something?
--
For technical support contracts, goto https://order.mysql.com/?ref=ensita
This email is sponsored by Ensita.net http://www.ensita.net/
__ ___ ___ __
/ |/ /_ __/ __/ __ \/ /Egor Egorov
/ /|_/ / // /\ \/ /_/ / /__ [EMAIL PROTECTED]
/_/ /_/\_, /___/\___\_\___/ MySQL AB / Ensita.net
___/ www.mysql.com
-
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
