----- Original Message -----
From: "Martin Gallagher" <[EMAIL PROTECTED]>
To: <mysql@lists.mysql.com>
Sent: Saturday, April 08, 2006 6:34 PM
Subject: COUNT() Efficiency
Hi,
If I did a query like:
SELECT COUNT(id) AS count1, COUNT(id) AS count2 FROM table WHERE id<100
Would MySQL run the COUNT() calculation once or twice?
I don't know the answer to your question but why would you want to count in
the same column of the same table twice in the same query?
I'm not very knowledgeable about MySQL performance - I'm mostly a DB2 guy -
but doesn't MySQL have an Explain command that will tell you what access
path you are getting? If it does, your best bet would be to try your query
and do an Explain to see what it actually does; it should be pretty clear
whether the count() is being done once or twice.
--
Rhino
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