DATEPART (Transact-SQL)

Článek
08/12/2013

Returns an integer that represents the specified datepart of the specified date.

For an overview of all Transact-SQL date and time data types and functions, see Date and Time Data Types and Functions (Transact-SQL).

Topic link icon Transact-SQL Syntax Conventions

Syntax

DATEPART ( datepart , date )

Arguments

datepart
Is the part of date (a date or time value) for which an integer will be returned. The following table lists all valid datepart arguments. User-defined variable equivalents are not valid.

datepart	Abbreviations
year	yy, yyyy
quarter	qq, q
month	mm, m
dayofyear	dy, y
day	dd, d
week	wk, ww
weekday	dw
hour	hh
minute	mi, n
second	ss, s
millisecond	ms
microsecond	mcs
nanosecond	ns
TZoffset	tz
ISO_WEEK	isowk, isoww

date
Is an expression that can be resolved to a time, date, smalldatetime, datetime, datetime2, or datetimeoffset value. date can be an expression, column expression, user-defined variable, or string literal.

To avoid ambiguity, use four-digit years. For information about two digits years, see Configure the two digit year cutoff Server Configuration Option.

Return Type

int

Return Value

Each datepart and its abbreviations return the same value.

The return value depends on the language environment set by using SET LANGUAGE and by the Configure the default language Server Configuration Option of the login. If date is a string literal for some formats, the return value depends on the format specified by using SET DATEFORMAT. SET DATEFORMAT does not affect the return value when the date is a column expression of a date or time data type.

The following table lists all datepart arguments with corresponding return values for the statement SELECT DATEPART(datepart,'2007-10-30 12:15:32.1234567 +05:10'). The data type of the date argument is datetimeoffset(7). The nanosecond datepart return value has a scale of 9 (.123456700) and the last two positions are always 00.

datepart	Return value
year, yyyy, yy	2007
quarter, qq, q	4
month, mm, m	10
dayofyear, dy, y	303
day, dd, d	30
week, wk, ww	45
weekday, dw	1
hour, hh	12
minute, n	15
second, ss, s	32
millisecond, ms	123
microsecond, mcs	123456
nanosecond, ns	123456700
TZoffset, tz	310

week and weekday datepart Arguments

When datepart is week (wk, ww) or weekday (dw), the return value depends on the value that is set by using SET DATEFIRST.

January 1 of any year defines the starting number for the week datepart, for example: DATEPART (wk, 'Jan 1, xxxx') = 1, where xxxx is any year.

The following table lists the return value for week and weekday datepart for '2007-04-21 ' for each SET DATEFIRST argument. January 1 is a Monday in the year 2007. April 21 is a Saturday in the year 2007. SET DATEFIRST 7, Sunday, is the default for U.S. English.

SET DATEFIRST argument	week returned	weekday returned
1	16	6
2	17	5
3	17	4
4	17	3
5	17	2
6	17	1
7	16	7

year, month, and day datepart Arguments

The values that are returned for DATEPART (year, date), DATEPART (month, date), and DATEPART (day, date) are the same as those returned by the functions YEAR, MONTH, and DAY, f respectively.

ISO_WEEK datepart

ISO 8601 includes the ISO week-date system, a numbering system for weeks. Each week is associated with the year in which Thursday occurs. For example, week 1 of 2004 (2004W01) ran from Monday 29 December 2003 to Sunday, 4 January 2004. The highest week number in a year might be 52 or 53. This style of numbering is typically used in European countries/regions, but rare elsewhere.

The numbering system in different countries/regions might not comply with the ISO standard. There are at least six possibilities as shown in the following table

First day of week	First week of year contains	Weeks assigned two times	Used by/in
Sunday	1 January, First Saturday, 1–7 days of year	Yes	United States
Monday	1 January, First Sunday, 1–7 days of year	Yes	Most of Europe and the United Kingdom
Monday	4 January, First Thursday, 4–7 days of year	No	ISO 8601, Norway, and Sweden
Monday	7 January, First Monday, 7 days of year	No
Wednesday	1 January, First Tuesday, 1–7 days of year	Yes
Saturday	1 January, First Friday, 1–7 days of year	Yes

TZoffset

The TZoffset (tz) is returned as the number of minutes (signed). The following statement returns a time zone offset of 310 minutes.

SELECT DATEPART (TZoffset, 2007-05-10  00:00:01.1234567 +05:10);

If the datepart argument is TZoffset (tz) and the date argument is not of datetimeoffset data type, NULL is returned.

smalldatetime date Argument

When date is smalldatetime, seconds are returned as 00.

Default Returned for a datepart That Is Not in a date Argument

If the data type of the date argument does not have the specified datepart, the default for that datepart will be returned only when a literal is specified for date.

For example, the default year-month-day for any date data type is 1900-01-01. The following statement has date part arguments for datepart, a time argument for date, and returns 1900, 1, 1, 1, 2.

SELECT DATEPART(year, '12:10:30.123')
    ,DATEPART(month, '12:10:30.123')
    ,DATEPART(day, '12:10:30.123')
    ,DATEPART(dayofyear, '12:10:30.123')
    ,DATEPART(weekday, '12:10:30.123');

If date is specified as a variable or table column and the data type for that variable or column does not have the specified datepart, error 9810 is returned. The following code example fails because the date part year is not a valid for the time data type that is declared for the variable @t.

DECLARE @t time = '12:10:30.123'; 
SELECT DATEPART(year, @t);

Fractional Seconds

Fractional seconds are returned as shown in the following statements:

SELECT DATEPART(millisecond, '00:00:01.1234567'); -- Returns 123
SELECT DATEPART(microsecond, '00:00:01.1234567'); -- Returns 123456
SELECT DATEPART(nanosecond,  '00:00:01.1234567'); -- Returns 123456700

Remarks

DATEPART can be used in the select list, WHERE, HAVING, GROUP BY and ORDER BY clauses.

In SQL Server 2012, DATEPART implicitly casts string literals as a datetime2 type. This means that DATEPART does not support the format YDM when the date is passed as a string. You must explicitly cast the string to a datetime or smalldatetime type to use the YDM format.

Examples

The following example returns the base year. The base year is useful for date calculations. In the example, the date is specified as a number. Notice that SQL Server interprets 0 as January 1, 1900.

SELECT DATEPART(year, 0), DATEPART(month, 0), DATEPART(day, 0);
-- Returns: 1900    1    1 */

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