Common PostgreSQL data operation notes: time

1. current time

select now();
select CURRENT_DATE;
select CURRENT_TIME;
select CURRENT_TIMESTAMP;
select CURRENT_TIME(precision);
select CURRENT_TIMESTAMP(precision);
select LOCALTIME;
select LOCALTIMESTAMP;
select LOCALTIME(precision);
select LOCALTIMESTAMP(precision);
 
-- Example 
SELECT CURRENT_TIME;
 result ：14:39:53.662522-05
 
SELECT CURRENT_DATE;
 result ：2001-12-23
 
SELECT CURRENT_TIMESTAMP;
 result ：2001-12-23 14:39:53.662522-05
 
SELECT CURRENT_TIMESTAMP(2);
 result ：2001-12-23 14:39:53.66-05
 
SELECT LOCALTIMESTAMP;
 result ：2001-12-23 14:39:53.662522

1.1. Time function

function	Return type	describe	Example	result
age(timestamp, timestamp)	interval	Subtract the parameter , Generate a usage year 、 month （ Not just days ） Of “ Symbolization ” Result	age(timestamp ‘2001-04-10’, timestamp ‘1957-06-13’)	43 year 9 month 27 Japan
age(timestamp)	interval	from current_date（ In the middle of the night ） subtract	age(timestamp ‘1957-06-13’)	43 years 8 mons 3 days
clock_timestamp()	timestamp with time zone	Current date and time （ Changes during statement execution ）; See the first 9.9.4 section
current_date	date	The current date ; See the first 9.9.4 section
current_time	time with time zone	current time （ Time of day ）; See the first 9.9.4 section
current_timestamp	timestamp with time zone	Current date and time （ When the current transaction starts ）; See the first 9.9.4 section
date_part(text, timestamp)	double precision	Get subdomain （ Equivalent to extract）; See the first 9.9.1 section	date_part(‘hour’, timestamp ‘2001-02-16 20:38:40’)	20
date_part(text, interval)	double precision	Get subdomain （ Equivalent to extract）; See the first 9.9.1 section	date_part(‘month’, interval ‘2 years 3 months’)	3
date_trunc(text, timestamp)	timestamp	Truncate to specified precision ; See also section 9.9.2 section	date_trunc(‘hour’, timestamp ‘2001-02-16 20:38:40’)	2001-02-16 20:00:00
date_trunc(text, interval)	interval	Truncate to specified precision ; See also section 9.9.2 section	date_trunc(‘hour’, interval ‘2 days 3 hours 40 minutes’)	2 days 03:00:00
extract(field from timestamp) double precision	Get subdomain ; See the first 9.9.1 section	extract(hour from timestamp ‘2001-02-16 20:38:40’)	20
extract(field from interval)	double precision	Get subdomain ; See the first 9.9.1 section	extract(month from interval ‘2 years 3 months’)	3
isfinite(date)	boolean	Test Limited Date （ No +/- Infinite ）	isfinite(date ‘2001-02-16’)	true
isfinite(timestamp)	boolean	Test finite timestamps （ No +/- Infinite ）	isfinite(timestamp ‘2001-02-16 21:28:30’)	true
isfinite(interval)	boolean	Test at finite intervals	isfinite(interval ‘4 hours’)	true
justify_days(interval)	interval	Adjust the interval like this 30 The day time period can be expressed as month	justify_days(interval ‘35 days’)	1 mon 5 days
justify_hours(interval)	interval	Adjust the interval like this 24 An hour time period can be expressed as a day	justify_hours(interval ‘27 hours’)	1 day 03:00:00
justify_interval(interval)	interval	Use justify_days and justify_hours Adjust the interval , Use extra symbols to adjust	justify_interval(interval ‘1 mon -1 hour’)	29 days 23:00:00
localtime	time	current time （ Time of day ）; See the first 9.9.4 section
localtimestamp	timestamp	Current date and time （ The start of the current transaction ）; See the first 9.9.4 section
make_date(year int, month int, day int)	date	From the year 、 month 、 Date of creation of the day field	make_date(2013, 7, 15)	2013-07-15
make_interval(years int DEFAULT 0, months int DEFAULT 0, weeks int DEFAULT 0, days int DEFAULT 0, hours int DEFAULT 0, mins int DEFAULT 0, secs double precision DEFAULT 0.0)	interval	From the year 、 month 、 Zhou 、 Japan 、 when 、 branch 、 Second field creation	interval make_interval(days => 10)	10 days
make_time(hour int, min int, sec double precision)	time	Since then 、 branch 、 Second field creation time	make_time(8, 15, 23.5)	08:15:23.5
make_timestamp(year int, month int, day int, hour int, min int, sec double precision)	timestamp	From the year 、 month 、 Japan 、 when 、 branch 、 Second field create timestamp	make_timestamp(2013, 7, 15, 8, 15, 23.5)	2013-07-15 08:15:23.5
make_timestamptz(year int, month int, day int, hour int, min int, sec double precision, [ timezone text ])	timestamp with time zone	From the year 、 month 、 Japan 、 when 、 branch 、 The second field creates a timestamp with a time zone . If not specified timezone, Use the current time zone .	make_timestamptz(2013, 7, 15, 8, 15, 23.5)	2013-07-15 08:15:23.5+01
now()	timestamp with time zone	Current date and time （ The start of the current transaction ）; See the first 9.9.4 section
statement_timestamp()	timestamp with time zone	Current date and time （ The start of the current transaction ）; See the first 9.9.4 section
timeofday()	text	Current date and time （ image clock_timestamp, But as a text character string ）; See the first 9.9.4 section
transaction_timestamp()	timestamp with time zone	Current date and time （ The start of the current transaction ）; See the first 9.9.4 section
to_timestamp(double precision)	timestamp with time zone	hold Unix Time （ from 1970-01-01 00:00:00+00 The first second ） convert to timestamp	to_timestamp(1284352323)	2010-09-13 04:32:03+00