PostgreSQL how to concat interval value '2 days'

Question

In PostgreSQL I want to concat the current_timestamp with an interval as follows:

select current_timestamp + interval 2||\' days\'
         


        

Answer 1

Please try this syntax:

select current_timestamp + ( 2 || ' days')::interval;

or even this one:

select current_timestamp + 2 * interval '1 day';

Answer 2

Part of the problem is that the standard SQL expression for intervals quotes the number, but not the keywords. So you have to be careful.

select current_date, current_date + interval '2' day;
--
2012-02-21   2012-02-23 00:00:00

In PostgreSQL, quoting like '2 day' and '2 days' also works. So you might think that '2' || ' days' would be equivalent, but it's not.

select current_date, current_date + interval '2' || ' days';
--
2012-02-21   2012-02-21 00:00:02 days

The solution, as A.H. said, is to cast the result string as an interval.

You can also use a variable in place of 2. This generates a calendar for 2012.

-- 0 to 365 is 366 days; 2012 is a leap year.
select ('2012-01-01'::date + (n || ' days')::interval)::date calendar_date
from generate_series(0, 365) n;

I use that final cast to date, because date + interval returns a timestamp.