postgresql 随机函数

随机函数

--function to get random number=============================================================
-- DROP FUNCTION IF EXISTS get_random_number(integer, integer);
CREATE OR REPLACE FUNCTION get_random_number(integer, integer) RETURNS integer AS
$BODY$
DECLARE
	start_int ALIAS FOR $1;
	end_int ALIAS FOR $2;
BEGIN
	RETURN trunc(random() * (end_int-start_int + 1) + start_int);
END;
$BODY$
LANGUAGE plpgsql;
--产生1-10之间的随机数（包括边缘）
--SELECT get_random_number(1, 10);

--function for get random date between start_date and end_date
-- DROP FUNCTION IF EXISTS get_random_date(date, date);
CREATE OR REPLACE FUNCTION get_random_date(start_date date, end_date date) RETURNS integer AS
$BODY$
DECLARE
	interval_days integer;
	random_days integer;
	random_date date;
BEGIN
	interval_days := end_date - start_date;
	random_days := get_random_number(0, interval_days);
	random_date := start_date + random_days;
	RETURN date_part('year', random_date) * 10000 + date_part('month', random_date) * 100 + date_part('day', random_date);
END;
$BODY$
LANGUAGE plpgsql;
-- SELECT get_random_date('2000-01-01', '2013-12-31');--result：201009