Help Center/ GaussDB(DWS)/ SQL Syntax Reference (8.1.3.x)/ Functions and Operators/ Date and Time Processing Functions and Operators/ EXTRACT
Updated on 2024-09-30 GMT+08:00
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EXTRACT

EXTRACT(field FROM source)

The extract function retrieves subcolumns such as year or hour from date/time values. source must be a value expression of type timestamp, time, or interval. (Expressions of type date are cast to timestamp and can therefore be used as well.) field is an identifier or string that selects what column to extract from the source value. The extract function returns values of type double precision. The following are valid field names:

century

Century

The first century starts at 0001-01-01 00:00:00 AD. This definition applies to all Gregorian calendar countries. There is no century number 0. You go from -1 century to 1 century.

Example:

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SELECT EXTRACT(century FROM TIMESTAMP '2000-12-16 12:21:13');
 date_part 
-----------
        20
(1 row)

day

  • For timestamp values, the day (of the month) column (1–31) 
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    SELECT EXTRACT(day FROM TIMESTAMP '2001-02-16 20:38:40');
 date_part 
-----------
        16
(1 row)
  • For interval values, the number of days 
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    SELECT EXTRACT(day FROM INTERVAL '40 days 1 minute');
 date_part 
-----------
        40
(1 row)

decade

Year column divided by 10

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SELECT EXTRACT(decade FROM TIMESTAMP '2001-02-16 20:38:40');
 date_part 
-----------
       200
(1 row)

dow

Day of the week as Sunday(0) to Saturday (6)

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SELECT EXTRACT(dow FROM TIMESTAMP '2001-02-16 20:38:40');
 date_part 
-----------
         5
(1 row)

doy

Day of the year (1–365 or 366)

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SELECT EXTRACT(doy FROM TIMESTAMP '2001-02-16 20:38:40');
 date_part 
-----------
        47
(1 row)
epoch
  • For timestamp with time zone values, the number of seconds since 1970-01-01 00:00:00 UTC (can be negative);

    for date and timestamp values, the number of seconds since 1970-01-01 00:00:00 local time;

    for interval values, the total number of seconds in the interval.

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    SELECT EXTRACT(epoch FROM TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40.12-08');
  date_part   
--------------
 982384720.12
(1 row)

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    SELECT EXTRACT(epoch FROM intervalL '5 days 3 hours');
 date_part 
-----------
    442800
(1 row)
  • Way to convert an epoch value back to a timestamp 
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    SELECT TIMESTAMP WITH TIME ZONE 'epoch' + 982384720.12 * interval '1 second' AS RESULT;
          result          
---------------------------
 2001-02-17 12:38:40.12+08
(1 row)

hour

Hour column (0–23)

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SELECT EXTRACT(hour FROM TIMESTAMP '2001-02-16 20:38:40');
 date_part 
-----------
        20
(1 row)

isodow

Day of the week (1–7)

Monday is 1 and Sunday is 7.

This is identical to dow except for Sunday.

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SELECT EXTRACT(isodow FROM TIMESTAMP '2001-02-18 20:38:40');
 date_part 
-----------
         7
(1 row)

isoyear

The ISO 8601 year that the date falls in (not applicable to intervals).

Each ISO year begins with the Monday of the week containing the 4th of January, so in early January or late December the ISO year may be different from the Gregorian year. See the week column for more information.

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SELECT EXTRACT(isoyear FROM DATE '2006-01-01');
 date_part 
-----------
      2005
(1 row)

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SELECT EXTRACT(isoyear FROM DATE '2006-01-02');
 date_part 
-----------
      2006
(1 row)

microseconds

The seconds column, including fractional parts, multiplied by 1,000,000

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SELECT EXTRACT(microseconds FROM TIME '17:12:28.5');
 date_part 
-----------
  28500000
(1 row)

millennium

Millennium

Years in the 1900s are in the second millennium. The third millennium started from January 1, 2001.

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SELECT EXTRACT(millennium FROM TIMESTAMP '2001-02-16 20:38:40');
 date_part 
-----------
         3
(1 row)

milliseconds

The seconds column, including fractional parts, multiplied by 1000. Note that this includes full seconds.

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SELECT EXTRACT(milliseconds FROM TIME '17:12:28.5');
 date_part 
-----------
     28500
(1 row)

minute

Minutes column (0–59)

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SELECT EXTRACT(minute FROM TIMESTAMP '2001-02-16 20:38:40');
 date_part 
-----------
        38
(1 row)

month

For timestamp values, the number of the month within the year (1–12);

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SELECT EXTRACT(month FROM TIMESTAMP '2001-02-16 20:38:40');
 date_part 
-----------
         2
(1 row)

For interval values, the number of months, modulo 12 (0–11)

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SELECT EXTRACT(month FROM interval '2 years 13 months');
 date_part 
-----------
         1
(1 row)

quarter

Quarter of the year (1–4) that the date is in

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SELECT EXTRACT(quarter FROM TIMESTAMP '2001-02-16 20:38:40');
 date_part 
-----------
         1
(1 row)

second

Seconds column, including fractional parts (0–59)

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SELECT EXTRACT(second FROM TIME '17:12:28.5');
 date_part 
-----------
      28.5
(1 row)

timezone

The time zone offset from UTC, measured in seconds. Positive values correspond to time zones east of UTC, negative values to zones west of UTC.

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SELECT EXTRACT(timezone FROM TIMETZ '17:12:28');
 date_part
-----------
    -36000
(1 row)

timezone_hour

The hour component of the time zone offset

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SELECT EXTRACT(timezone_hour FROM TIMETZ '17:12:28');
 date_part
-----------
       -10
(1 row)

timezone_minute

The minute component of the time zone offset

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SELECT EXTRACT(timezone_minute FROM TIMETZ '17:12:28');
 date_part
-----------
         0
(1 row)

week

The number of the week of the year that the day is in. By definition (ISO 8601), the first week of a year contains January 4 of that year. (The ISO-8601 week starts on Monday.) In other words, the first Thursday of a year is in week 1 of that year.

Because of this, it is possible for early January dates to be part of the 52nd or 53rd week of the previous year, and late December dates to be part of the 1st week of the next year. For example, 2005-01-01 is part of the 53rd week of year 2004, 2006-01-01 is part of the 52nd week of year 2005, and 2012-12-31 is part of the 1st week of year 2013. You are advised to use the columns isoyear and week together to ensure consistency.

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SELECT EXTRACT(week FROM TIMESTAMP '2001-02-16 20:38:40');
 date_part 
-----------
         7
(1 row)

year

Year column

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SELECT EXTRACT(year FROM TIMESTAMP '2001-02-16 20:38:40');
 date_part 
-----------
      2001
(1 row)