Re: Index suggestion needed for performance improvement

[Ronald Brown]

Rick James Wrote:
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> * Use VARCHAR, not CHAR, unless the string is
> really fixed length.
>
> * Remove LEFT, it seems to be irrelevant.

you mean something like this

UPDATE users u,( SELECT count(content.record_num) as pdfs_uploaded_count, content.uploader as uploader
FROM users, content
WHERE content.anonymous = 0
AND content.uploader != 0
AND users.record_num = content.uploader
GROUP BY users.record_num) as s
SET u.pdfs_uploaded = s.pdfs_uploaded_count
WHERE u.record_num = s.uploader

If i use count(*) , how would mysql know which table to get count from ?