Group mysql query by 15 min intervals

Question

I\'ve got a monitoring system that is collecting data every n seconds (n is approximately 10 but varies). I\'d like to aggregate the collected data by 15 minute intervals.

Answer 1

Adaptation of approach 1) below:

select Round(date_format(date, "%i") / (15*60)) AS interval  
from table
group by interval 

Adaptation of approach 3) below:

SELECT Round(Convert(substring(date_column, 14, 2), UNSIGNED) / (15*60)) AS interval /* e.g. 2009-01-04 12:20:00 */
FROM table 
GROUP BY interval;

A few approaches I've found here:

1)

select date_format(date, "%W") AS `Day of the week`, sum(cost)
from daily_cost
group by `Day of the week` 
order by date_format(date, "%w")

2)

select count(*) as 'count', 
  date_format(min(added_on), '%Y-%M-%d') as 'week commencing',
  date_format(added_on, '%Y%u') as 'week' 
from system 
where added_on >= '2007-05-16' 
group by week 
order by 3 desc;

3)

SELECT substring(postdate, 1,10) AS dd, COUNT(id) FROM MyTable GROUP BY dd;

(Also here: http://www.bradino.com/mysql/dayparting-on-datetime-field-using-substring/)

EDIT: All the solutions will perform badly on a table with a large number of records.