Performance tuning a group by with percentage

Running MySql 5.0.85, I need to be as efficient as possible about a
few queries. If I could get a little review, I would appreciate it.

I collect data in the millions, and need the top 50 grouped by one
field, with a percentage of how much those top 50 occupy.

Here is what I have come up with... 1) I have a feeling I can be more
efficient, perhaps with a join 2) How can I get the percentage to be
of precision in the hundredths, so * 100.00 ie: .07 becomes 7.00,
getting SQL errors if I (percentage * 100)

SELECT user_agent_parsed, user_agent_original,
COUNT( user_agent_parsed ) AS thecount,
COUNT( * ) / ( SELECT COUNT( * ) FROM agents ) AS percentage
FROM agents
GROUP BY user_agent_parsed
ORDER BY thecount DESC LIMIT 50;
Second issue, once a day I need to archive the result of the above.
Any suggestions on how to best to do that? I can schedule with cron,
or in my case, launchd, unless someone has a better suggestion.

Would you think that a simple 'SELECT (the above) INTO foo' would
suffice? ( I will add a date stamp as well )



Thanks all.

--
Scott * If you contact me off list replace talklists@ with scott@ *


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