Sliding window aggregate Big Query 15 minute aggregation - time-series

Question

I have a table like this
Row time viewCount
1 00:00:00 31
2 00:00:01 44
3 00:00:02 78
4 00:00:03 71
5 00:00:04 72
6 00:00:05 73
7 00:00:06 64
8 00:00:07 70
I would like to aggregate this into
Row time viewCount
1 00:00:00 31
2 00:15:00 445
3 00:30:00 700
4 00:45:00 500
5 01:00:04 121
6 01:15:00 475
.
.
.
Please help. Thanks in advance

Answer 1

Supposing that you actually have a TIMESTAMP column, you can use an approach like this:
#standardSQL
SELECT
TIMESTAMP_SECONDS(
UNIX_SECONDS(timestamp) -
MOD(UNIX_SECONDS(timestamp), 15 * 60)
) AS time,
SUM(viewCount) AS viewCount
FROM `project.dataset.table`
GROUP BY time;
It relies on conversion to and from Unix seconds in order to compute the 15 minute intervals. Note that it will not produce a row with a zero count for an empty 15 minute interval unlike Mikhail's solution, however (it's not clear if this is important to you).

Answer 2

Below is for BigQuery Standard SQL
Note: you provided simplified example of your data and below follows it - so instead of each 15 minutes aggregation, it uses each 2 sec aggregation. This is for you to be able to easy test / play with it. It is easily can be adjusted to 15 minutes by changing SECOND to MINUTE in 3 places and 2 to 15 in 3 places. Also this example uses TIME data type for time field as it is in your example so it is limited to just 24 hour period - most likely in your real data you have DATETIME or TIMESTAMP. In this case you will also need to replace all TIME_* functions with respective DATETIME_* or TIMESTAMP_* functions
So, finally - the query is:
#standardSQL
WITH `project.dataset.table` AS (
SELECT TIME '00:00:00' time, 31 viewCount UNION ALL
SELECT TIME '00:00:01', 44 UNION ALL
SELECT TIME '00:00:02', 78 UNION ALL
SELECT TIME '00:00:03', 71 UNION ALL
SELECT TIME '00:00:04', 72 UNION ALL
SELECT TIME '00:00:05', 73 UNION ALL
SELECT TIME '00:00:06', 64 UNION ALL
SELECT TIME '00:00:07', 70
),
period AS (
SELECT MIN(time) min_time, MAX(time) max_time, TIME_DIFF(MAX(time), MIN(time), SECOND) diff
FROM `project.dataset.table`
),
checkpoints AS (
SELECT TIME_ADD(min_time, INTERVAL step SECOND) start_time, TIME_ADD(min_time, INTERVAL step + 2 SECOND) end_time
FROM period, UNNEST(GENERATE_ARRAY(0, diff + 2, 2)) step
)
SELECT start_time time, SUM(viewCount) viewCount
FROM checkpoints c
JOIN `project.dataset.table` t
ON t.time >= c.start_time AND t.time < c.end_time
GROUP BY start_time
ORDER BY start_time, time
and result is:
Row time viewCount
1 00:00:00 75
2 00:00:02 149
3 00:00:04 145
4 00:00:06 134