Postgres INTERVAL using value from table

Question

If I want to add 5 days to a date, I can do it using the INTERVAL function:

select create_ts + interval \'5 days\' from abc_company;
         


        

Answer 1

here is a function that I use:

CREATE OR REPLACE FUNCTION DateAdd(diffType varchar(15), incrementValue int, inputDate timestamp) RETURNS timestamp AS $$
DECLARE
   YEAR_CONST Char(15) := 'year';
   MONTH_CONST Char(15) := 'month';
   WEEK_CONST Char(15) := 'week';
   DAY_CONST Char(15) := 'day';
   HOUR_CONST Char(15) := 'hour';

   dateTemp timestamp;
   intervals interval;
BEGIN
    IF lower($1) = lower(YEAR_CONST) THEN
        select cast(cast(incrementvalue as character varying) || ' year' as interval) into intervals;
    ELSEIF lower($1) = lower(MONTH_CONST) THEN
        select cast(cast(incrementvalue as character varying) || ' months' as interval) into intervals;
    ELSEIF lower($1) = lower(DAY_CONST) THEN
        select cast(cast(incrementvalue as character varying) || ' day' as interval) into intervals;
    ELSEIF lower($1) = lower(WEEK_CONST) THEN
        select cast(cast(incrementvalue as character varying) || ' week' as interval) into intervals;
    ELSEIF lower($1) = lower(HOUR_CONST) THEN
        select cast(cast(incrementvalue as character varying) || ' hour' as interval) into intervals;
    END IF;

   dateTemp := inputdate + intervals;

   RETURN dateTemp;
END;
$$ LANGUAGE plpgsql;

Used like so:

select dateadd('day', 3, current_timestamp);

It supports adding years, months, weeks, days, hours. More support could be added