Preamble
PostgreSQL date_part function extracts parts from the date.
The syntax of the date_part function in PostgreSQL
date_part( 'unit', date )
Parameters and function arguments
- date – Date, timestamp, time, or interval value from which part of the date is to be extracted.
- Unit – Type of the unit of the interval measurement, such as day, month, minute, hour, etc. E. This may be one of the following:
unit
|
Explanation
|
---|---|
century
|
Uses the Gregorian calendar, where the first century begins with ‘0001-01-01 00:00:00 AD’.
|
day
|
day of the month (1 to 31)
|
decade
|
The year is divided by 10
|
dow
|
day per week (0=Sunday, 1=Monday, 2=Tuesday,… 6=Saturday)
|
doy
|
day of the week in a year (1 = first day of the year, 365/366 = last day of the year, depending on whether it is a leap year)
|
epoch
|
Number of seconds from ‘1970-01-01 00:00:00 UTC’ if the date value. The number of seconds in an interval, if the value is an interval.
|
hour
|
hour (0 to 23)
|
isodow
|
day of the week (1=Monday, 2=Tuesday, 3=Wednesday,… 7=Sunday)
|
isoyear
|
ISO 8601 (where the year begins on Monday of the week containing January 4)
|
microseconds
|
Seconds (and fractions of a second) multiplied by 1,000,000
|
millennium
|
millennium significance
|
milliseconds
|
Seconds (and fractions of a second) multiplied by 1000
|
minute
|
minute (0 to 59)
|
month
|
month number for the month (from 1 to 12), if the date value. Number of months (from 0 to 11), if the value of the interval
|
quarter
|
a quarter (1 to 4)
|
second
|
seconds (and fractions of a second)
|
timezone
|
Time zone offset from UTC, expressed in seconds
|
timezone_hour
|
Time zone offset from UTC
|
timezone_minute
|
Minute time zone offset from UTC
|
week
|
Weekly number of the year based on ISO 8601 (where the year starts on Monday of the week containing January 4)
|
the year
|
year as 4 digits
|
The date_part function can be used in the following PostgreSQL versions
PostgreSQL 11, PostgreSQL 10, PostgreSQL 9.6, PostgreSQL 9.5, PostgreSQL 9.4, PostgreSQL 9.3, PostgreSQL 9.2, PostgreSQL 9.1, PostgreSQL 9.0, PostgreSQL 8.4.
|
Consider some examples of the date_part function to understand how to use the date_part function in PostgreSQL with date values.
For example:
SELECT date_part('day', date '2019-04-25');
--Result: 25
SELECT date_part('month', date '2019-04-23');
--Result: 4
SELECT date_part('year', date '2019-04-23');
--Result: 2019
Let’s see how to use the date_part function in PostgreSQL with timestamp values.
For example:
SELECT date_part('day', timestamp '2019-04-23 08:44:21');
--Result: 23
SELECT date_part('month', timestamp '2019-04-23 08:44:21');
--Result: 4
SELECT date_part('minute', timestamp '2019-04-23 08:44:21');
--Result: 44
SELECT date_part('hour', timestamp '2019-04-23 08:44:21');
--Result: 8
Let’s see how to use the date_part function in PostgreSQL with time values.
For example:
SELECT date_part('minute', time '08:44:21');
--Result: 44
SELECT date_part('milliseconds', time '08:44:21.7');
--Result: 21700
Let’s see how to use the date_part function in PostgreSQL with interval values.
For example:
SELECT date_part('day', interval '8 days 4 hours');
--Result: 8
SELECT date_part('hour', interval '8 days 4 hours');
--Result: 4
Date functions in PostgreSQL , Time functions in PostgreSQL
About Enteros
Enteros offers a patented database performance management SaaS platform. It proactively identifies root causes of complex business-impacting database scalability and performance issues across a growing number of clouds, RDBMS, NoSQL, and machine learning database platforms.
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