Re: Takers for a Friday SQL puzzle? Timestamps and recursion...

[Tonkuma]

cast(hour(event _ts) as char(2)) || ':' ||

cast(15*(minute (event_ts)/15) as char(2))

I didn't use simple "cast(hour(even t_ts) as char(2))" in my post
appended to Lennart's.
I used rather complicated following expression
SUBSTR(DIGITS(H OUR(event_times tamp)),9,2)

The reason is to consider hours less than 9(single digit).
(and for 0 minute.)
If event_ts = '2008-05-10 09:02:27.578658 ',
your expression and my expression return:

VALUES cast(hour('2008-05-10 09:02:27.578658 ') as char(2)) || ':' ||
cast(15*(minute ('2008-05-10 09:02:27.578658 ')/15) as char(2));
------------------------------------------------------------------

1
-----
9 :0

1 record(s) selected.


VALUES SUBSTR(DIGITS(H OUR('2008-05-10 09:02:27.578658 ')),9,2)||':'||
SUBSTR(DIGITS(M INUTE('2008-05-10 09:02:27.578658 ')/15*15),
9,2)||':00';
--------------------------------------------------------------------

1
--------
09:00:00

1 record(s) selected.


Grouping must be done correctly by your expression.
But, grouping by two separate expressions would be also worth to
consider.
GROUP BY
HOUR(event_time stamp)
, MINUTE(event_ti mestamp)/15