DATEADD

MSSQL
select dateadd(year,1, '2004-2-29')

PostgreSQL
select '2004-2-29'::date + cast('1 years' as interval)

MSSQL:
select dateadd(month,1,'2004-2-29')


PostgreSQL:
select '2004-2-29'::date + cast('1 months' as interval)

MSSQL:
select dateadd(month,1, '1976-11-05 6:29 AM')

PostgreSQL:
select '2006-01-06 6:29 AM'::timestamptz + cast('1 months' as interval)

MSSQL:
select dateadd(day,1,'2006-01-06 6:29 AM')
-- or --
select convert(datetime,'2006-01-06 6:29 AM') + 1


PosgtgreSQL:
select '2006-01-06 6:29 AM'::timestamp + cast('1 days' as interval);

------------------------------------------------------------------------
------------------------------------------------------------------------
MS SQL equivalent compatible DATEADD function

-- Function: dateadd(character varying, integer, date)

-- DROP FUNCTION dateadd(character varying, integer, date);

CREATE OR REPLACE FUNCTION dateadd(character varying, integer, date)
RETURNS date AS
$BODY$

DECLARE
p_Interval ALIAS FOR $1;
p_N ALIAS FOR $2;
p_Date ALIAS FOR $3;




BEGIN
if p_Interval = 'm' then
return p_Date + cast(p_N || ' months' as interval);
elseif p_Interval = 'y' then
return p_Date + cast(p_N || ' years' as interval);
else
raise exception 'dateadd interval parameter not supported';
-- raise exception 'hello';
return null;
end if;
END;
$BODY$
LANGUAGE 'plpgsql';