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PostgreSQL extract function
PostgreSQL extract function extracts parts from the date.
Syntax of the extract function in PostgreSQL
extract( unit from date )
Parameters and function arguments
- date – date, timestamp, time, or interval value from which a part of the date is to be extracted.
- Unit – Type of the unit of interval measurement, such as day, month, minute, hour, etc. 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 extract function can be used in future versions of PostgreSQL
| 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. |
Let’s look at some examples of extract functions to see how to use the extract function in PostgreSQL with date values
For example:
SELECT extract(day from date '2019-04-23');
--Result: 25
SELECT extract(month from date '2019-04-23');
--Result: 4
SELECT extract(year from date '2019-04-23');
--Result: 2019
Let’s see how to use the extract function in PostgreSQL with timestamp values.
For example:
SELECT extract(day from timestamp '2019-04-23 08:44:21');
--Result: 23
SELECT extract(month from timestamp '2019-04-23 08:44:21');
--Result: 4
SELECT extract(minute from timestamp '2019-04-23 08:44:21');
--Result: 44
SELECT extract(hour from timestamp '2019-04-23 08:44:21');
--Result: 8
Let’s see how to use the extract function in PostgreSQL with time values.
For example:
SELECT extract(minute from time '08:44:21');
--Result: 44
SELECT extract(milliseconds from time '08:44:21.7');
--Result: 21700
Let’s see how to use the extract function in PostgreSQL with interval values.
For example:
SELECT extract(day from interval '5 days 3 hours');
--Result: 5
SELECT extract(hour from interval '5 days 3 hours');
--Result: 3
Calculate Age with PostgreSQL with age() and extract() functions
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