postgres通过开始时间，结束时间获得 几天几小时几分钟几秒

select getMedianTime('2021-09-04 06:16:41'::TIMESTAMP,'2021-09-04 07:20:42'::TIMESTAMP)

create or replace function getMedianTime(starttime TIMESTAMP,endtime TIMESTAMP)
returns varchar as $$
declare
	p_day integer;
	p_hour integer;
	p_minute integer;
	p_second integer;
	sumTime varchar;
begin

	sumTime := '';
	p_day := (select extract(day FROM (age(endtime, starttime))));
	if p_day <> 0 then
		sumTime := sumTime || p_day || '天';
	else
		sumTime := sumTime || '0天';
	end if;
	
	p_hour := (select extract(hour FROM (age(endtime, starttime))));
	if p_hour <> 0 then
		sumTime := sumTime || p_hour || '时';
	else
		sumTime := sumTime || '0时';
	end if;
	
	p_minute := (select extract(minute FROM (age(endtime, starttime))));
	if p_minute <> 0 then
		sumTime := sumTime || p_minute || '分钟';
	else
		sumTime := sumTime || '0分钟';
	end if;
	
	p_second := (select extract(second FROM (age(endtime, starttime))));
	if p_second <> 0 then
		sumTime := sumTime || p_second || '秒';
	else
		sumTime := sumTime || '0秒';
	end if;
 return sumTime;
end; $$
language plpgsql;