DateTime Functions and Operators¶

• Note : Example result may be various based on time zone.

add_days(date date|timestamp, day int)¶

Returns date value which is added with given day parameter.

Parameters:	date – base timestamp or date day – day value to be added
Return type:	timestamp
Example:

select add_days(date '2013-12-30', 5);
> 2014-01-03 15:00:00

select add_days(timestamp '2013-12-05 12:10:20', -7);
> 2013-11-28 03:10:20

add_months(date date|timestamp, month int)¶

Returns date value which is added with given month parameter.

Parameters:	date – base timestamp or date month – month value to be added
Return type:	timestamp
Example:

select add_months(date '2013-12-17', 2);
> 2014-02-16 15:00:00

current_date()¶

Returns current date

Return type:	date

select current_date();
> 2014-09-23

current_time()¶

Returns current time

Return type:	time

select current_time();
> 05:18:27.651999

extract(field FROM source)¶

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

century

The century

select extract(century from timestamp '2001-12-16 12:21:13');
> 21.0

The first century starts at 0001-01-01 00:00:00 AD, although they did not know it at the time. This definition applies to all Gregorian calendar countries. There is no century number 0, you go from -1 century to 1 century. If you disagree with this, please write your complaint to: Pope, Cathedral Saint-Peter of Roma, Vatican.

day

For timestamp values, the day (of the month) field (1 - 31)

select extract(day from timestamp '2001-02-16 20:38:40');
> 16.0

decade

The year field divided by 10

select extract(decade from timestamp '2001-02-16 20:38:40');
> 200.0

dow

The day of the week as Sunday(0) to Saturday(6)

select extract(dow from timestamp '2001-02-16 20:38:40');
> 5.0

Note that extract’s day of the week numbering differs from that of the to_char(..., ‘D’) function.

doy

The day of the year (1 - 365/366)

select extract(doy from timestamp '2001-02-16 20:38:40');
> 47.0

hour

The hour field (0 - 23)

select extract(hour from timestamp '2001-02-16 20:38:40');
> 20.0

isodow

The day of the week as Monday(1) to Sunday(7)

select extract(isodow from timestamp '2001-02-18 20:38:40');
> 7.0

This is identical to dow except for Sunday. This matches the ISO 8601 day of the week numbering.

isoyear

The ISO 8601 year that the date falls in

select extract(isoyear from date '2006-01-01');
> 2005.0

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 field for more information.

microseconds

The seconds field, including fractional parts, multiplied by 1 000 000; note that this includes full seconds

select extract(microseconds from time '17:12:28.5');
> 2.85E7

millennium

The millennium

select extract(millennium from timestamp '2001-02-16 20:38:40');
> 3.0

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

milliseconds

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

select extract(milliseconds from time '17:12:28.5');
> 28500.0

minute

The minutes field (0 - 59)

select extract(minute from timestamp '2001-02-16 20:38:40');
> 38.0

month

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

select extract(month from timestamp '2001-02-16 20:38:40');
> 2.0

quarter

The quarter of the year (1 - 4) that the date is in

select extract(quarter from timestamp '2001-02-16 20:38:40');
> 1.0

second

The seconds field, including fractional parts (0 - 59[1])

select extract(second from timestamp '2001-02-16 20:38:40');
> 40.0

week

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

In the ISO definition, it is possible for early-January dates to be part of the 52nd or 53rd week of the previous year, and for late-December dates to be part of the first week of the next year. For example, 2005-01-01 is part of the 53rd week of year 2004, and 2006-01-01 is part of the 52nd week of year 2005, while 2012-12-31 is part of the first week of 2013. It’s recommended to use the isoyear field together with week to get consistent results.

select extract(week from timestamp '2001-02-16 20:38:40');
> 7.0

year

The year field. Keep in mind there is no 0 AD, so subtracting BC years from AD years should be done with care.

select extract(year from timestamp '2001-02-16 20:38:40');
> 2001.0

The extract function is primarily intended for computational processing.

The date_part function is also supported. It is equivalent to the SQL-standard function extract:

date_part('field', source)¶

Note that here the field parameter needs to be a string value, not a name. The valid field names for date_part are the same as for extract.

select date_part('day', timestamp '2001-02-16 20:38:40');
> 16.0

now()¶

Returns current timestamp

Return type:	timestamp
Example:

select now();
> 2014-09-23 08:32:43.286

to_char(src timestamp, format text)¶

Converts timestamp to text. For more detailed, see ‘Date/Time Formatting and Conversion’ section below.

Parameters:	src – timestamp to be converted format – format string
Return type:	text

select to_char(current_timestamp, 'yyyy-MM-dd');
> 2014-09-23

to_date(src text, format text)¶

Converts text to date. For more detailed, see ‘Date/Time Formatting and Conversion’ section below.

Parameters:	src – date string to be converted format – format string
Return type:	date

select to_date('2014-01-04', 'YYYY-MM-DD');
> 2014-01-04

to_timestamp(epoch int)¶

Converts int(UNIX epoch) to timestamp.

Parameters:	epoch – second value from Jan. 1, 1970
Return type:	timestamp

select to_timestamp(412312345);
> 1983-01-25 03:12:25

to_timestamp(src text, format text)

Converts text timestamp. For more detailed, see ‘Date/Time Formatting and Conversion’ section below.

Parameters:	src – timestamp string to be converted format – format string
Return type:	timestamp

select to_timestamp('97/2/16 8:14:30', 'FMYYYY/FMMM/FMDD FMHH:FMMI:FMSS');
> 0097-02-15 23:14:30

utc_usec_to(string text, long timestamp, int dayOfWeek)¶

• If the first parameter is ‘day’.

  Shifts and return a UNIX timestamp in microseconds to the beginning of the day it occurs in. For example, if unix_timestamp occurs on May 19th at 08:58, this function returns a UNIX timestamp for May 19th at 00:00 (midnight).

• If the first parameter is ‘hour’.

  Shifts and return a UNIX timestamp in microseconds to the beginning of the hour it occurs in. For example, if unix_timestamp occurs at 08:58, this function returns a UNIX timestamp for 08:00 on the same day.

• If the first parameter is ‘month’.

  Shifts and return a UNIX timestamp in microseconds to the beginning of the month it occurs in. For example, if unix_timestamp occurs on March 19th, this function returns a UNIX timestamp for March 1st of the same year.

• If the first parameter is ‘year’.

  Returns a UNIX timestamp in microseconds that represents the year of the unix_timestamp argument. For example, if unix_timestamp occurs in 2010, the function returns 1274259481071200, the microsecond representation of 2010-01-01 00:00.

• If the first parameter is ‘week’ and third parameter is 2 i.e (TUESDAY)

  Returns a UNIX timestamp in microseconds that represents a day in the week of the For example, if unix_timestamp occurs on Friday, 2008-04-11, and you set day_of_week to 2 (Tuesday), the function returns a UNIX timestamp for Tuesday, 2008-04-08.

Parameters:	string – could be ‘day’ ‘hour’ ‘month’ ‘year’ ‘week’ long – unix timestamp in microseconds int – day of the week from 0 (Sunday) to 6 (Saturday).Optional parameter required only if first parameter is ‘week’
Return type:	long
Example:

SELECT utc_usec_to('day', 1274259481071200);
> 1274227200000000