Performance tuning a group by with percentage

[Scott Haneda]

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@ *