


How to Generate a Running Row Count in PostgreSQL for Each Minute, Including Inactive Minutes?
PostgreSQL: Generating a Running Row Count by Minute, Including Inactive Periods
This article demonstrates how to generate a running count of rows in a PostgreSQL table for each minute, even if some minutes have no activity.
Method 1: Running Count for Active Minutes Only
This approach uses window functions to calculate a running count for each minute where activity exists:
SELECT DISTINCT date_trunc('minute', "when") AS minute, count(*) OVER (ORDER BY date_trunc('minute', "when")) AS running_count FROM mytable ORDER BY 1;
date_trunc('minute', "when")
groups rows by minute. The count(*) OVER (ORDER BY date_trunc('minute', "when"))
function provides a running total ordered by minute.
Method 2: Including Inactive Minutes
To include minutes with zero activity, we use generate_series
to create a complete minute sequence and a LEFT JOIN
to incorporate the counts:
WITH cte AS ( SELECT date_trunc('minute', "when") AS minute, COUNT(*) AS minute_ct FROM mytable GROUP BY 1 ) SELECT m.minute, COALESCE(sum(cte.minute_ct) OVER (ORDER BY m.minute), 0) AS running_count FROM ( SELECT generate_series(min(minute), max(minute), interval '1 min') AS minute FROM cte ) m LEFT JOIN cte USING (minute) ORDER BY 1;
A CTE (cte
) groups rows by minute and counts them. generate_series
creates a series of minutes spanning the entire time range. The LEFT JOIN
combines this series with the counts from cte
, and COALESCE
handles minutes with no activity by assigning a running count of 0. The sum() OVER (ORDER BY m.minute)
then calculates the cumulative sum.
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