目录

时间/日期操作符

日期/时间函数

EXTRACT函数

综合示例

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时间/日期操作符

 

操作符	例子	结果
+	date '2011-09-28' + integer '7'	date '2011-10-05'
+	date '2011-09-18' + interval '1 hour'	timestamp '2011-09-18 01:00'
+	date '2011-09-18' + time '02:00'	timestamp '2011-09-18 02:00'
+	interval '1 day' + interval '1 hour'	interval '1 day 01:00'
+	timestamp '2011-09-28 01:00' + interval '23 hours'	timestamp '2011-09-29 00:00'
+	time '01:00' + interval '3 hours'	time '04:00'
-	- interval '23 hours'	interval '-23:00'
-	date '2001-10-01' - date '2001-09-28'	integer '3'
-	date '2011-10-01' - integer '7'	date '2011-09-24'
-	date '2011-09-28' - interval '1 hour'	timestamp '2011-09-27 23:00'
-	time '05:00' - time '03:00'	interval '02:00'
-	time '05:00' - interval '2 hours'	time '03:00'
-	timestamp '2011-09-28 23:00' - interval '23 hours'	timestamp '2011-09-28 00:00'
-	interval '1 day' - interval '1 hour'	interval '23:00'
-	timestamp '2001-09-29 03:00' - timestamp '2001-09-27 12:00'	interval '1 day 15:00'
*	interval '1 hour' * double precision '3.5'	interval '03:30'
/	interval '1 hour' / double precision '1.5'	interval '00:40'

 

日期/时间函数

函数	返回类型	描述	例子	结果
age(timestamp, timestamp)	interval	减去参数，生成一个使用年、月的"符号化"的结果	age('2001-04-10', timestamp '1957-06-13')	43 years 9 mons 27 days
age(timestamp)	interval	从current_date减去得到的数值	age(timestamp '1957-06-13')	43 years 8 mons 3 days
current_date	date	今天的日期
current_time	time	现在的时间
current_timestamp	timestamp	日期和时间
date_part(text, timestamp)	double	获取子域(等效于extract)	date_part('hour', timestamp '2012-05-06 10:20:30')	10
date_part(text, interval)	double	获取子域(等效于extract)	date_part('month', interval '2 years 3 months')	3
date_trunc(text, timestamp)	timestamp	截断成指定的精度	date_trunc('hour', timestamp '2012-05-06 10:20:30')	2012-05-06 10:00:00+00
extract(field from timestamp)	double	获取子域	extract(hour from timestamp '2012-05-06 10:20:30')	10
extract(field from interval)	double	获取子域	extract(month from interval '2 years 3 months')	3
localtime	time	今日的时间
localtimestamp	timestamp	日期和时间
now()	timestamp	当前的日期和时间(等效于 current_timestamp)
timeofday()	text	当前日期和时间

 

EXTRACT函数

用于取出时间中的一部分，比如取出小时部分，参数示例如下：

域	描述	例子	结果
CENTURY	世纪	EXTRACT(CENTURY FROM TIMESTAMP '2000-12-16 12:21:13');	20
DAY	(月分)里的日期域(1-31)	EXTRACT(DAY from TIMESTAMP '2001-02-16 20:38:40');	16
DECADE	年份域除以10	EXTRACT(DECADE from TIMESTAMP '2001-02-16 20:38:40');	200
DOW	每周的星期号(0-6；星期天是0) (仅用于timestamp)	EXTRACT(DOW FROM TIMESTAMP '2001-02-16 20:38:40');	5
DOY	一年的第几天(1 -365/366) (仅用于 timestamp)	EXTRACT(DOY from TIMESTAMP '2001-02-16 20:38:40');	47
HOUR	小时域(0-23)	EXTRACT(HOUR from TIMESTAMP '2001-02-16 20:38:40');	20
MICROSECONDS	秒域，包括小数部分，乘以 1,000,000。	EXTRACT(MICROSECONDS from TIME '17:12:28.5');	28500000
MILLENNIUM	千年	EXTRACT(MILLENNIUM from TIMESTAMP '2001-02-16 20:38:40');	3
MILLISECONDS	秒域，包括小数部分，乘以 1000。	EXTRACT(MILLISECONDS from TIME '17:12:28.5');	28500
MINUTE	分钟域(0-59)	EXTRACT(MINUTE from TIMESTAMP '2001-02-16 20:38:40');	38
MONTH	对于timestamp数值，它是一年里的月份数(1-12)；对于interval数值，它是月的数目，然后对12取模(0-11)	EXTRACT(MONTH from TIMESTAMP '2001-02-16 20:38:40');	2
QUARTER	该天所在的该年的季度(1-4)(仅用于 timestamp)	EXTRACT(QUARTER from TIMESTAMP '2001-02-16 20:38:40');	1
SECOND	秒域，包括小数部分(0-59[1])	EXTRACT(SECOND from TIMESTAMP '2001-02-16 20:38:40');	40
WEEK	该天在所在的年份里是第几周。	EXTRACT(WEEK from TIMESTAMP '2001-02-16 20:38:40');	7
YEAR	年份域	EXTRACT(YEAR from TIMESTAMP '2001-02-16 20:38:40');	2001

 

综合示例

获取当前据本周五23:59还有多少小时多少分钟

select EXTRACT(HOUR FROM(CURRENT_DATE + time '23:59') - CURRENT_TIMESTAMP) + (6 - extract(dow from current_date) )*24 "hour",

EXTRACT(MINUTE FROM(CURRENT_DATE + time '23:59') - CURRENT_TIMESTAMP) "minute";