How to aggregate rows in the range of timestamp in vertica db (vsql) - sql

Question

Suppose I have a table with data like this:
ts | bandwidth_bytes
---------------------+-----------------
2021-08-27 22:00:00 | 3792
2021-08-27 21:45:00 | 1164
2021-08-27 21:30:00 | 7062
2021-08-27 21:15:00 | 3637
2021-08-27 21:00:00 | 2472
2021-08-27 20:45:00 | 1328
2021-08-27 20:30:00 | 1932
2021-08-27 20:15:00 | 1434
2021-08-27 20:00:00 | 1530
2021-08-27 19:45:00 | 1457
2021-08-27 19:30:00 | 1948
2021-08-27 19:15:00 | 1160
I need to output something like this:
ts | bandwidth_bytes
---------------------+-----------------
2021-08-27 22:00:00 | 15,655
2021-08-27 21:00:00 | 7166
2021-08-27 20:00:00 | 6095
I want to do sum bandwidth_bytes over 1 hour timestamp of data.
I want to do this in vsql specifically.
More columns are present but for simplification I have shown only these two.

Answer 1

You can use date_trunc():
select [date_trunc('hour', ts)][1] as ts_hh, sum(bandwidth_bytes)
from t
group by ts_hh;

Answer 2

Use Vertica's lovely function TIME_SLICE().
You can't only go by hour, you can also go by slices of 2 or 3 hours, which DATE_TRUNC() does not offer.
You seem to want all between 20:00:01 and 21:00:00 to belong to a time slice of 21:00:00. In both DATE_TRUNC() and TIME_SLICE(), however, it's 20:00:00 to 20:59:59 that belongs to the same time slice. So I subtracted one second before applying TIME_SLICE() .
WITH
-- your in data ...
indata(ts,bandwidth_bytes) AS (
SELECT TIMESTAMP '2021-08-27 22:00:00',3792
UNION ALL SELECT TIMESTAMP '2021-08-27 21:45:00',1164
UNION ALL SELECT TIMESTAMP '2021-08-27 21:30:00',7062
UNION ALL SELECT TIMESTAMP '2021-08-27 21:15:00',3637
UNION ALL SELECT TIMESTAMP '2021-08-27 21:00:00',2472
UNION ALL SELECT TIMESTAMP '2021-08-27 20:45:00',1328
UNION ALL SELECT TIMESTAMP '2021-08-27 20:30:00',1932
UNION ALL SELECT TIMESTAMP '2021-08-27 20:15:00',1434
UNION ALL SELECT TIMESTAMP '2021-08-27 20:00:00',1530
UNION ALL SELECT TIMESTAMP '2021-08-27 19:45:00',1457
UNION ALL SELECT TIMESTAMP '2021-08-27 19:30:00',1948
UNION ALL SELECT TIMESTAMP '2021-08-27 19:15:00',1160
)
SELECT
TIME_SLICE(ts - INTERVAL '1 SECOND' ,1,'HOUR','END') AS ts
, SUM(bandwidth_bytes) AS bandwidth_bytes
FROM indata
GROUP BY 1
ORDER BY 1 DESC;
ts | bandwidth_bytes
---------------------+-----------------
2021-08-27 22:00:00 | 15655
2021-08-27 21:00:00 | 7166
2021-08-27 20:00:00 | 6095