Counting users online with last hour

[Mark Jerzykowski]

Hi,

I have a log table which contains the fields log_time (DATETIME) and
session_id (VARCHAR). Using these 2 columns I want to be able to SELECT the
number of users who have been online during the past hour. Getting the
number of rows logged in the last hour is easy but I can't work out how to
only count distinct session_id entries.

Thanks,

Mark
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[Mark Jerzykowski]

Not to worry. I think I've worked it out:

SELECT COUNT( DISTINCT (
session_id
) )
FROM log
WHERE DATE_SUB( CURDATE( ) , INTERVAL 30
DAY ) <= log_date

Mark

"Mark Jerzykowski" <ma************ **@ntlworld.com > wrote in message
news:Ge******** *******@newsfe2-gui.ntli.net...

Hi,

I have a log table which contains the fields log_time (DATETIME) and
session_id (VARCHAR). Using these 2 columns I want to be able to SELECT the number of users who have been online during the past hour. Getting the
number of rows logged in the last hour is easy but I can't work out how to
only count distinct session_id entries.

Thanks,

Mark
---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.737 / Virus Database: 491 - Release Date: 11/08/2004

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[Bill Karwin]

Mark Jerzykowski wrote:

I have a log table which contains the fields log_time (DATETIME) and
session_id (VARCHAR). Using these 2 columns I want to be able to SELECT the
number of users who have been online during the past hour. Getting the
number of rows logged in the last hour is easy but I can't work out how to
only count distinct session_id entries.

Mark J. posted one method, but here is another for comparison:

SELECT MAX(log_time), session_id
FROM myTable
WHERE log_time > now() - interval 60 minute
GROUP BY session_id;

Regards,
Bill K.