Does the order of conditions in a WHERE clause affect MySQL performance?
- by Greg
Say that I have a long, expensive query, packed with conditions, searching a large number of rows. I also have one particular condition, like a company id, that will limit the number of rows that need to be searched considerably, narrowing it down to dozens from hundreds of thousands.
Does make any difference to MySQL performance whether I do this:
SELECT * FROM clients WHERE
(firstname LIKE :foo OR lastname LIKE :foo OR phone LIKE :foo) AND
(firstname LIKE :bar OR lastname LIKE :bar OR phone LIKE :bar) AND
company = :ugh
or this:
SELECT * FROM clients WHERE
company = :ugh AND
(firstname LIKE :foo OR lastname LIKE :foo OR phone LIKE :foo) AND
(firstname LIKE :bar OR lastname LIKE :bar OR phone LIKE :bar)
