Alex Pilson wrote:
I have this query below than seems to be running really slow. I have tried indexing key JOIN fields but it seems to have not helped. Any pointers would be greatly appreciated.
(ver: MySQL 3.23.53) side note: seems to run fairly quick in 4.0.18
SELECT
dl.email as download_email, CONCAT(dl.first, " ", dl.last) as download_name, o.id as orderID,
c.id as cust_id, dl.id as dlId, c.email as customer_email
FROM download_users as dl
LEFT JOIN orders as o ON dl.email = o.email LEFT JOIN customers as c ON (dl.email=c.email OR c.id = o.cust_id OR concat(dl.first, dl.last) = concat(c.bill_first,c.bill_last))
GROUP BY download_email
ORDER BY orderID DESC, cust_id DESC
As far as I know, MySQL 3.23 doesn't use index for a query with OR clause (exept rare cases). so you end up with a full table scan.. (quiet slow, isn't it ?). I don't see anything to speed this up.
-- Philippe Poelvoorde COS Trading Ltd.
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