【PostgreSQL】时间戳处理相关函数和操作

Operator	Example	Result
+	date '2001-09-28' + integer '7'	date '2001-10-05'
+	date '2001-09-28' + interval '1 hour'	timestamp '2001-09-28 01:00:00'
+	date '2001-09-28' + time '03:00'	timestamp '2001-09-28 03:00:00'
+	interval '1 day' + interval '1 hour'	interval '1 day 01:00:00'
+	timestamp '2001-09-28 01:00' + interval '23 hours'	timestamp '2001-09-29 00:00:00'
+	time '01:00' + interval '3 hours'	time '04:00:00'
-	- interval '23 hours'	interval '-23:00:00'
-	date '2001-10-01' - date '2001-09-28'	integer '3' (days)
-	date '2001-10-01' - integer '7'	date '2001-09-24'
-	date '2001-09-28' - interval '1 hour'	timestamp '2001-09-27 23:00:00'
-	time '05:00' - time '03:00'	interval '02:00:00'
-	time '05:00' - interval '2 hours'	time '03:00:00'
-	timestamp '2001-09-28 23:00' - interval '23 hours'	timestamp '2001-09-28 00:00:00'
-	interval '1 day' - interval '1 hour'	interval '1 day -01:00:00'
-	timestamp '2001-09-29 03:00' - timestamp '2001-09-27 12:00'	interval '1 day 15:00:00'
*	900 * interval '1 second'	interval '00:15:00'
*	21 * interval '1 day'	interval '21 days'
*	double precision '3.5' * interval '1 hour'	interval '03:30:00'
/	interval '1 hour' / double precision '1.5'	interval '00:40:00'

常用函数

函数	返回类型	描述	样例	结果
age(timestamp, timestamp)	interval	返回两个时间戳之间相差的年月天数	age(timestamp '2001-04-10', timestamp '1957-06-13')	43 years 9 mons 27 days
age(timestamp)	interval	返回现在的时间与参数的中时间戳的差值	age(timestamp '1957-06-13')	43 years 8 mons 3 days
extract(field from timestamp)	double precision	得到时间戳里的任意一个值，比如年，月或日	extract(hour from timestamp '2001-02-16 20:38:40')	20
make_date(year int, month int, day int)	date	自己创建一个日期包含 year, month and day fields	make_date(2013, 7, 15)	2013-07-15
make_timestamp(year int, month int, day int, hour int, min int, sec double precision)	timestamp	自己创建一个时间戳包含year, month, day, hour, minute and seconds fields	make_timestamp(2013, 7, 15, 8, 15, 23.5)	2013-07-15 08:15:23.5
now()	timestamp with time zone	此时此刻的时间戳
to_timestamp(double precision)	timestamp with time zone	将格林尼治时间秒转化为时间戳 ( 秒是从 1970-01-01 00:00:00+00开始计的)	to_timestamp(1284352323)	2010-09-13 04:32:03+00