How to Get Start and End Date of Window Interval in ksqlDB

You can use WINDOWSTART and WINDOWEND to get the starting and ending timestamps from each window interval.

The e xample below shows starting window times, but the same applies to ending times:

SELECT
  WINDOWSTART, -- BIGINT
  FROM_UNIXTIME(WINDOWSTART), -- TIMESTAMP
  subreddit,
  MAX(active_user_count) as max_activity
FROM REDDIT
WINDOW TUMBLING (SIZE 1 HOUR)
GROUP BY SUBREDDIT
EMIT CHANGES;

that returns :

+---------------+-------------------------+------------+--------------+
|WINDOWSTART    |WINDOWSTART_AS_TIMESTAMP |SUBREDDIT   |MAX_ACTIVITY  |
+---------------+-------------------------+------------+--------------+
|1608804000000  |2020-12-24T10:00:00.000  |science     |479           |
|1608804000000  |2020-12-24T10:00:00.000  |arts        |24            |
|1608804000000  |2020-12-24T10:00:00.000  |technology  |98            |
|1608804000000  |2020-12-24T10:00:00.000  |news        |86            |

Note that WINDOWSTART and WINDOWEND are of type BIGINT. You can use FROM_UNIXTIME() to have them converted to TIMESTAMP values.

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