PostgreSQL JUSTIFY_INTERVAL() Function

Summary: in this tutorial, you will learn how to use the PostgreSQL JUSTIFY_INTERVAL() to adjust an interval.

Introduction to the PostgreSQL JUSTIFY_INTERVAL() function

The JUSTIFY_INTERVAL() function allows you to adjust an interval by converting days exceeding 30 days into months and hours exceeding 24 hours into days. It essentially normalizes an interval for enhanced readability.

The JUSTIFY_INTERVAL() function achieves this by utilizing the JUSTIFY_DAYS() and JUSTIFY_HOURS() functions, with additional sign adjustments:

• JUSTIFY_DAYS(): Convert days exceeding 30 days into months and remaining days.
• JUSTIFY_HOURS(): Convert hours exceeding 24 hours into days and remaining hours.

Here’s the syntax of the JUSTIFY_INTERVAL() function:

JUSTIFY_INTERVAL( value ) → interval

In this syntax, the value parameter is an interval value you want to justify.

The JUSTIFY_INTERVAL() function returns an adjusted interval by:

• Convert days exceeding 30 days into months and remaining days.
• Convert hours exceeding 24 hours into days and remaining hours.
• Correct signs (positive or negative) for the overall duration.

PostgreSQL JUSTIFY_INTERVAL() function examples

Let’s take some examples of using the JUSTIFY_INTERVAL() function.

1) Basic JUSTIFY_INTERVAL() function examples

The following example uses the JUSTIFY_INTERVAL() function to justify an interval in days to months:

SELECT JUSTIFY_INTERVAL('35 days');

Output:

justify_interval
------------------
 1 mon 5 days
(1 row)

The following statement uses the JUSTIFY_INTERVAL() function to justify an interval in hours to days:

SELECT JUSTIFY_INTERVAL('30 hours');

Output:

justify_interval
------------------
 1 day 06:00:00
(1 row)

2) Using the JUSTIFY_INTERVAL() function with negative intervals

The following example uses the JUSTIFY_INTERVAL() function to convert a negative interval into hours days and hours:

SELECT JUSTIFY_INTERVAL('-2 days 5 hours');

Output:

justify_interval
-------------------
 -1 days -19:00:00
(1 row)

In this example:

• -2 days 5 hours is -48 hours + 5 hours which is 43 hours.
• The function converts – 43 hours to -24 hours + – 19 hours, which results in -1 days -19:00:00.

Summary

• Use the JUSTIFY_INTERVAL() function to normalize an interval by converting days exceeding 30 days into months and hours exceeding 24 hours into days, while maintaining correct signs for positive or negative intervals.