-- Each Date Part can be either singular or plural
-- In this example, YEAR or YEARS can be used interchangeably
-- 1 year
SELECT INTERVAL 1 YEAR;
-- 1 year
SELECT INTERVAL 1 YEARS;
-- The number used to specify an interval can optionally be wrapped in single quotes
-- 28 days
SELECT INTERVAL '28' DAYS;
-- The number and date part can optionally be wrapped entirely in single quotes
-- 28 days
SELECT INTERVAL '28 DAYS';
-- Intervals can also be used to specify a time period rather than a date period
-- 00:00:30
SELECT INTERVAL 30 SECONDS;

-- Intervals can also be produced as a result of a timestamp operator like subtraction
-- These can include a date and time component on the Interval
-- 1 day 01:00:00
SELECT '2022-01-02 01:00:00'::TIMESTAMP - '2022-01-01'::TIMESTAMP;

-- WARNING: If a decimal value is specified, it will be automatically truncated to an integer
-- To use more precise values, simply use a more granular date part 
-- (In this example use 18 MONTHS instead of 1.5 YEARS)
-- The statement below is equivalent to to_years(CAST(1.5 AS INTEGER))
-- 1 year
SELECT INTERVAL '1.5' YEARS; --WARNING! This returns 1 year!