From: Warren Young
Date: September 14 2010 10:24pm
Subject: Re: Get the number of rows with a "used" query.
List-Archive: http://lists.mysql.com/plusplus/9048
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Please keep your replies on the list.

> As a simple workaround could you just do a "SELECT COUNT(*) FROM"
> query first if you really need to know how many rows are being
> returned.
> =20
> That exactly what I did !
> Problem was : by making a "select count(*) from (myquery) as t" , =
before  actually using the query, double the global amount of time for =
the query ...

It shouldn't double the processing time.  First, there's less IPC I/O to =
return just a count than the millions of rows.  Second, if your WHERE =
clause columns are all indexed, the DB server can answer the COUNT() =
query without even scanning the tables, just by looking at the indexes.=

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