Literal INTERVAL

A literal INTERVAL specifies the value of an INTERVAL data type, including its qualifying time-units.

The following examples each use a literal INTERVAL as an expression: 
INSERT INTO manufact VALUES ('CAT', 'Catwalk Sports', 
   INTERVAL (16) DAY TO DAY);

SELECT lead_time + INTERVAL (5) DAY TO DAY FROM manufact;

The second example adds five days to each value of lead_time selected from the manufact table.

For more information, see Literal INTERVAL.