Help Center> GaussDB(DWS)> 8.1.3 Recommended> Functions and Operators> Date and Time Processing Functions and Operators> Time/Date functions
Updated on 2024-05-31 GMT+08:00
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Time/Date functions

age(timestamp, timestamp)

Description: Subtracts arguments, producing a result in YYYY-MM-DD format. If the result is negative, the returned result is also negative.

Return type: interval

Example:

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SELECT age(TIMESTAMP '2001-04-10', TIMESTAMP '1957-06-13');
           age           
-------------------------
 43 years 9 mons 27 days
(1 row)

age(timestamp)

Description: Subtracts from current_date

Return type: interval

Example:

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SELECT age(TIMESTAMP '1957-06-13');
           age           
-------------------------
 60 years 2 mons 18 days
(1 row)

adddate(date, interval | int)

Description: Returns the result of a given datetime plus the time interval of a specified unit. The default unit is day (when the second parameter is an integer).

Return type: timestamp

Example:

When the input parameter is of the text type:

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SELECT adddate('2020-11-13', 10);
  adddate
------------
 2020-11-23
(1 row)

SELECT adddate('2020-11-13', interval '1' month);
  adddate
------------
 2020-12-13
(1 row)

SELECT adddate('2020-11-13 12:15:16', interval '1' month);
       adddate
---------------------
 2020-12-13 12:15:16
(1 row)


SELECT adddate('2020-11-13', interval '1' minute);
       adddate
---------------------
 2020-11-13 00:01:00
(1 row)

When the input parameter is of the date type:

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SELECT adddate(current_date, 10);
  adddate
------------
 2021-09-24
(1 row)

SELECT adddate(date '2020-11-13', interval '1' month);
       adddate
---------------------
 2020-12-13 00:00:00
(1 row)

subdate(date, interval | int)

Description: Returns the result of a given datetime minus the time interval of a specified unit. The default unit is day (when the second parameter is an integer).

Return type: timestamp

Example:

When the input parameter is of the text type:

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SELECT subdate('2020-11-13', 10);
  subdate
------------
 2020-11-03
(1 row)

SELECT subdate('2020-11-13', interval '2' month);
  subdate
------------
 2020-09-13
(1 row)

SELECT subdate('2020-11-13 12:15:16', interval '1' month);
       subdate
---------------------
 2020-10-13 12:15:16
(1 row)

SELECT subdate('2020-11-13', interval '2' minute);
       subdate
---------------------
 2020-11-12 23:58:00
(1 row)

When the input parameter is of the date type:

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SELECT subdate(current_date, 10);
  subdate
------------
 2021-09-05
(1 row)

SELECT subdate(current_date, interval '1' month);
       subdate
---------------------
 2021-08-15 00:00:00
(1 row)

date_add(date, interval)

Description: Returns the result of a given datetime plus the time interval of a specified unit. It is equivalent to adddate(date, interval | int).

Return type: timestamp

date_sub(date, interval)

Description: Returns the result of a given datetime minus the time interval of a specified unit. It is equivalent to subdate(date, interval | int).

Return type: timestamp

timestampadd(field, numeric, timestamp)

Description: Adds an integer interval in the unit of field (the number of seconds can be a decimal) to a datetime expression. If the value is negative, the corresponding time interval is subtracted from the given datetime expression. The field can be year, month, quarter, day, week, hour, minute, second, and microsecond.

Return type: timestamp

Example:

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SELECT timestampadd(year, 1, TIMESTAMP '2020-2-29');
    timestampadd
---------------------
 2021-02-28 00:00:00
(1 row)

SELECT timestampadd(second, 2.354156, TIMESTAMP '2020-11-13');
        timestampadd
----------------------------
 2020-11-13 00:00:02.354156
(1 row)

timestampdiff(field, timestamp1, timestamp2)

Description: Subtracts timestamp1 from timestamp2 and returns the difference in the unit of field. If the difference is negative, this function returns it normally. The field can be year, month, quarter, day, week, hour, minute, second, or microsecond.

Return type: bigint

Example:

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SELECT timestampdiff(day, TIMESTAMP '2001-02-01', TIMESTAMP '2003-05-01 12:05:55');
 timestampdiff 
---------------
      819
(1 row)

clock_timestamp()

Description: Specifies the current timestamp of the real-time clock.

Return type: timestamp with time zone

Example:

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SELECT clock_timestamp();
        clock_timestamp        
-------------------------------
 2017-09-01 16:57:36.636205+08
(1 row)

current_date

Description: Current date

Return type: date

Example:

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SELECT current_date;
    date    
------------
 2017-09-01
(1 row)

current_time

Description: Current time

Return type: time with time zone

Example:

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SELECT current_time;
       timetz       
--------------------
 16:58:07.086215+08
(1 row)

current_timestamp

Description: Specifies the current date and time.

Return type: timestamp with time zone

Example:

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SELECT current_timestamp;
       pg_systimestamp        
------------------------------
 2017-09-01 16:58:19.22173+08
(1 row)

datediff(date1, date2)

Description: Returns the number of days between two given dates.

Return type: integer

Example:

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SELECT datediff(date '2020-11-13', date '2012-10-16');
 datediff
----------
     2950
(1 row)

date_part(text, timestamp)

Description: Obtains the precision specified by text.

Equals extract(field from timestamp).

Return type: double precision

Example:

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

date_part(text, interval)

Description: Obtains the precision specified by text. If the value is greater than 12, obtain the remainder after it is divided by 12.

Equals extract(field from timestamp)

Return type: double precision

Example:

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SELECT date_part('month', interval '2 years 3 months');
 date_part 
-----------
         3
(1 row)

date_trunc(text, timestamp)

Description: Truncates to the precision specified by text.

Return type: timestamp

Example:

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SELECT date_trunc('hour', TIMESTAMP  '2001-02-16 20:38:40');
     date_trunc      
---------------------
 2001-02-16 20:00:00
(1 row)

-- Obtain the last day of last year.
SELECT date_trunc('day', date_trunc('year',CURRENT_DATE)+ '-1');
       date_trunc
------------------------
 2022-12-31 00:00:00+00
(1 row)

-- Obtain the first day of this year.
SELECT date_trunc('year',CURRENT_DATE);
       date_trunc
------------------------
 2023-01-01 00:00:00+00
(1 row)

-- Obtain the first day of last year.
SELECT date_trunc('year',now() + '-1 year');
       date_trunc
------------------------
 2022-01-01 00:00:00+00
(1 row)

trunc(timestamp)

Description: By default, the data is intercepted by day.

Return type: timestamp

Example:

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SELECT trunc(TIMESTAMP  '2001-02-16 20:38:40');                                                                                                                                                                   trunc
---------------------
2001-02-16 00:00:00
(1 row)

extract(field from timestamp)

Description: Obtains the value of field with the specified precision. For details about the valid values of field, see EXTRACT.

Return type: double precision

Example:

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

extract(field from interval)

Description: Obtains the value of field with the specified precision. If the value is greater than 12, obtain the remainder after it is divided by 12. For details about the valid values of field, see EXTRACT.

Return type: double precision

Example:

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SELECT extract(month FROM interval '2 years 3 months');
 date_part 
-----------
         3
(1 row)

day(date)

Description: Obtains the number of days in the month in which date is located. This function is the same as the dayofmonth function.

Value range: 1 to 31

Return type: integer

Example:

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SELECT day('2020-06-28');
 day
-----
  28
(1 row)

dayofmonth(date)

Description: Obtains the number of days in the month in which date is located.

Value range: 1 to 31

Return type: integer

Example:

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SELECT dayofmonth('2020-06-28');
 dayofmonth
------------
         28
(1 row)

dayofweek(date)

Description: Returns the week index corresponding to the given date, with Sunday as the start day of the week.

Value range: 1 to 7

Return type: integer

Example:

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SELECT dayofweek('2020-11-22');
 dayofweek
-----------
         1
(1 row)

dayofyear(date)

Description: Returns the number of days of a given date in the current year.

Value range: 1 to 366

Return type: integer

Example:

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SELECT dayofyear('2020-02-29');
 dayofyear
-----------
        60
(1 row)

hour(timestamp with time zone)

Description: Obtains the hour value in the time.

Return type: integer

Example:

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SELECT hour(timestamptz '2018-12-13 12:11:15+06');
 hour
------
   6
(1 row)

isfinite(date)

Description: Checks whether a date is finite.

Return type: boolean

Example:

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SELECT isfinite(date '2001-02-16');
 isfinite 
----------
 t
(1 row)
SELECT isfinite(date 'infinity');
 isfinite
----------
 f
(1 row)

isfinite(timestamp)

Description: Checks whether a timestamp is finite.

Return type: boolean

Example:

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SELECT isfinite(timestamp '2001-02-16 21:28:30');
 isfinite 
----------
 t
(1 row)
SELECT isfinite(timestamp 'infinity');
 isfinite
----------
 f
(1 row)

isfinite(interval)

Description: Checks whether an interval is finite.

Return type: boolean

Example:

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SELECT isfinite(interval '4 hours');
 isfinite 
----------
 t
(1 row)

justify_days(interval)

Description: Adjusts interval to 30-day time periods are represented as months

Return type: interval

Example:

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SELECT justify_days(interval '35 days');
 justify_days 
--------------
 1 mon 5 days
(1 row)

justify_hours(interval)

Description: Adjusts interval to 24-hour time periods are represented as days

Return type: interval

Example:

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SELECT justify_hours(interval '27 HOURS');
 justify_hours  
----------------
 1 day 03:00:00
(1 row)

justify_interval(interval)

Description: Adjusts interval using justify_days and justify_hours.

Return type: interval

Example:

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SELECT justify_interval(interval '1 MON -1 HOUR');
 justify_interval 
------------------
 29 days 23:00:00
(1 row)

localtime

Description: Current time

Return type: time

Example:

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SELECT localtime ;
     time
----------------
 16:05:55.664681
(1 row)

localtimestamp

Description: Specifies the current date and time.

Return type: timestamp

Example:

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SELECT localtimestamp;
         timestamp          
----------------------------
 2017-09-01 17:03:30.781902
(1 row)

makedate(year, dayofyear)

Description: Returns a date value based on the given year and the number of days in a year.

Return type: date

Example:

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SELECT makedate(2020, 60);
  makedate
------------
 2020-02-29
(1 row)

maketime(hour, minute, second)

Description: Returns a value of the time type based on the given hour, minute, and second. The value of the time type in GaussDB(DWS) ranges from 00:00:00 to 24:00:00. Therefore, this function is not available when the value of hour is greater than 24 or less than 0.

Return type: time

Example:

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SELECT maketime(12, 15, 30.12);
  maketime
-------------
 12:15:30.12
(1 row)

microsecond(timestamp with time zone)

Description: Obtains the microsecond value in the time.

Return type: integer

Example:

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SELECT microsecond(timestamptz '2018-12-13 12:11:15.123634+06');
 microsecond
-------------
      123634
(1 row)

minute(timestamp with time zone)

Description: Obtains the minute value in the time.

Return type: integer

Example:

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SELECT minute(timestamptz '2018-12-13 12:11:15+06');
 minute
--------
     11
(1 row)

month(date)

Description: Returns the month of a given datetime.

Return type: integer

Example:

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SELECT month('2020-11-30');
 month
-------
    11
(1 row)

now([fsp])

Description: Specifies the start time of the transaction. The parameter determines the microsecond output precision. The default value is 6.

Return type: timestamp with time zone

Example:

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SELECT now();
              now              
-------------------------------
 2017-09-01 17:03:42.549426+08
(1 row)

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SELECT now(3);
             now    
---------------------------- 
 2021-09-08 10:59:00.427+08
(1 row)

numtodsinterval(num, interval_unit)

Description: Converts a number to the interval type. num is a numeric-typed number. interval_unit is a string in the following format: 'DAY' | 'HOUR' | 'MINUTE' | 'SECOND'

You can set the IntervalStyle parameter to oracle to be compatible with the interval output format of the function in the Oracle database.

Example:

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SELECT numtodsinterval(100, 'HOUR');
 numtodsinterval 
-----------------
 100:00:00
(1 row)

SET intervalstyle = oracle;
SET
SELECT numtodsinterval(100, 'HOUR');
        numtodsinterval
-------------------------------
 +000000004 04:00:00.000000000
(1 row)

pg_sleep(seconds)

Description: Pauses the current session for a specified number of seconds.

Return type: void

Example:

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SELECT pg_sleep(10);
 pg_sleep 
----------

(1 row)

period_add(P, N)

Description: Returns the date of a given period plus N months.

Return type: integer

Example:

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SELECT period_add(200801, 2);
 period_add
------------
     200803
(1 row)

period_diff(P1, P2)

Description: Returns the number of months between two given dates.

Return type: integer

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SELECT period_diff(200802, 200703);
 period_diff
-------------
          11
(1 row)

quarter(date)

Description: Obtains the quarter to which the date belongs.

Return type: integer

Example:

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SELECT quarter(date '2018-12-13');
 quarter
---------
       4
(1 row)

second(timestamp with time zone)

Description: Obtains the second value in the time.

Return type: integer

Example:

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SELECT second(timestamptz '2018-12-13 12:11:15+06');
 second
--------
     15
(1 row)

statement_timestamp()

Description: Specifies the current date and time.

Return type: timestamp with time zone

Example:

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SELECT statement_timestamp();
      statement_timestamp      
-------------------------------
 2017-09-01 17:04:39.119267+08
(1 row)

sysdate

Description: Specifies the current date and time.

Return type: timestamp

Example:

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SELECT sysdate;
       sysdate       
---------------------
 2017-09-01 17:04:49
(1 row)

timeofday()

Description: Current date and time (like clock_timestamp, but returned as a text string)

Return type: text

Example:

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SELECT timeofday();
              timeofday              
-------------------------------------
 Fri Sep 01 17:05:01.167506 2017 CST
(1 row)

transaction_timestamp()

Description: Current date and time (equivalent to current_timestamp)

Return type: timestamp with time zone

Example:

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SELECT transaction_timestamp();
     transaction_timestamp     
-------------------------------
 2017-09-01 17:05:13.534454+08
(1 row)

from_unixtime(unix_timestamp[,format])

Description: Converts a Unix timestamp to the datetime type when the format string is set to the default value. If the format string is specified, convert the Unix timestamp to a string of a specified format.

Return type: timestamp (default format string) or text (specified format string)

Example:

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SELECT from_unixtime(875996580);
    from_unixtime
---------------------
 1997-10-04 20:23:00
(1 row)
SELECT from_unixtime(875996580, '%Y %D %M %h:%i:%s');
       from_unixtime
---------------------------
 1997 4th October 08:23:00
(1 row)

unix_timestamp([timestamp with time zone])

Description: Obtains the number of seconds from '1970-01-01 00:00:00'UTC to the time when the parameter is input. If no parameter is input, set this parameter to the current time.

Return type: bigint (no parameter is input) or numeric (parameter is input)

Example:

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SELECT unix_timestamp();
 unix_timestamp
----------------
     1693906219
(1 row)

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SELECT unix_timestamp('2018-09-08 12:11:13+06');
 unix_timestamp
----------------
     1536387073.000000
(1 row)

add_months(d,n)

Description: Calculates the time point day and time of nth months.

Return type: timestamp

Example:

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SELECT add_months(to_date('2017-5-29', 'yyyy-mm-dd'), 11);
     add_months      
---------------------
 2018-04-29 00:00:00
(1 row)

last_day(d)

Description: Calculates the time of the last day in the month.

  • In the ORA- or TD-compatible mode, the return type is timestamp.
  • In the MySQL-compatible mode, the return type is date.

Example:

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SELECT last_day(to_date('2017-01-01', 'YYYY-MM-DD')) AS cal_result;
     cal_result      
---------------------
 2017-01-31 00:00:00
(1 row)

next_day(x,y)

Description: Calculates the time of the next week y started from x

  • In the ORA- or TD-compatible mode, the return type is timestamp.
  • In the MySQL-compatible mode, the return type is date.

Example:

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SELECT next_day(TIMESTAMP '2017-05-25 00:00:00','Sunday')AS cal_result;
     cal_result      
---------------------
 2017-05-28 00:00:00
(1 row)

from_days(days)

Description: Returns the corresponding date value based on the given number of days.

Return type: date

Example:

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SELECT from_days(730669);
 from_days
------------
 2000-07-03
(1 row)

to_days(timestamp)

Description: Returns the number of days from the first day of year 0 to a specified date.

Return type: integer

Example:

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SELECT to_days(TIMESTAMP '2008-10-07');
 to_days
---------
  733687
(1 row)