til/postgres/different-ways-to-define-an-interval.md

Different Ways To Define An Interval

There are several different ways in PostgreSQL to define an interval data type. An interval is useful because it can represent a discrete chunk of time. This is handy for doing date math.

Here are four different ways to define an interval:

1. Use the interval keyword with a string

> select interval '3 days';
 interval
----------
 3 days
(1 row)

2. Cast a string to the interval type

> select '3 days'::interval;
 interval
----------
 3 days
(1 row)

3. The @ operator is a finicky syntax for declaring an interval

> select @ 3 days;
 days
------
    3
(1 row)

4. The make_interval function can take various forms of arguments to construct an interval

> select make_interval(days => 3);
 make_interval
---------------
 3 days
(1 row)

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