GENERATE_SERIES

Generates a dataset starting from a specified point, ending at another specified point, and optionally with an incrementing value. The GENERATE_SERIES function works with the following data types:

• Integer
• Date
• Timestamp

Syntax

GENERATE_SERIES(<start>, <stop>[, <step_interval>])

Arguments

Argument	Description
start	The starting value, representing the first number, date, or timestamp in the sequence.
stop	The ending value, representing the last number, date, or timestamp in the sequence.
step_interval	The step interval, determining the difference between adjacent values in the sequence. For integer sequences, the default value is 1. For date sequences, the default step interval is 1 day. For timestamp sequences, the default step interval is 1 microsecond.

note

When dealing with functions like GENERATE_SERIES and RANGE, a key distinction lies in their boundary traits. GENERATE_SERIES is bound by both the left and right sides, while RANGE is bound on the left side only. For example, utilizing RANGE(1, 11) is equivalent to GENERATE_SERIES(1, 10).

Return Type

Returns a list containing a continuous sequence of numeric values, dates, or timestamps from start to stop.

Examples

Example 1: Generating Numeric, Date, and Timestamp Data

SELECT * FROM GENERATE_SERIES(1, 10, 2);

generate_series|
---------------+
              1|
              3|
              5|
              7|
              9|

SELECT * FROM GENERATE_SERIES('2023-03-20'::date, '2023-03-27'::date);

generate_series|
---------------+
     2023-03-20|
     2023-03-21|
     2023-03-22|
     2023-03-23|
     2023-03-24|
     2023-03-25|
     2023-03-26|
     2023-03-27|

SELECT * FROM GENERATE_SERIES('2023-03-26 00:00'::timestamp, '2023-03-27 12:00'::timestamp, 86400000000);

generate_series    |
-------------------+
2023-03-26 00:00:00|
2023-03-27 00:00:00|

Example 2: Filling Query Result Gaps

This example uses the GENERATE_SERIES function and left join operator to handle gaps in query results caused by missing information in specific ranges.

CREATE TABLE t_metrics (
  date Date,
  value INT
);

INSERT INTO t_metrics VALUES
  ('2020-01-01', 200),
  ('2020-01-01', 300),
  ('2020-01-04', 300),
  ('2020-01-04', 300),
  ('2020-01-05', 400),
  ('2020-01-10', 700);

SELECT date, SUM(value), COUNT() FROM t_metrics GROUP BY date ORDER BY date;

date      |sum(value)|count()|
----------+----------+-------+
2020-01-01|       500|      2|
2020-01-04|       600|      2|
2020-01-05|       400|      1|
2020-01-10|       700|      1|

To close the gaps between January 1st and January 10th, 2020, use the following query:

SELECT t.date, COALESCE(SUM(t_metrics.value), 0), COUNT(t_metrics.value)
FROM generate_series(
  '2020-01-01'::Date,
  '2020-01-10'::Date
) AS t(date)
LEFT JOIN t_metrics ON t_metrics.date = t.date
GROUP BY t.date ORDER BY t.date;

date      |coalesce(sum(t_metrics.value), 0)|count(t_metrics.value)|
----------+---------------------------------+----------------------+
2020-01-01|                              500|                     2|
2020-01-02|                                0|                     0|
2020-01-03|                                0|                     0|
2020-01-04|                              600|                     2|
2020-01-05|                              400|                     1|
2020-01-06|                                0|                     0|
2020-01-07|                                0|                     0|
2020-01-08|                                0|                     0|
2020-01-09|                                0|                     0|
2020-01-10|                              700|                     1|