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datetime (Transact-SQL)

  • Artikkeli

Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance Azure Synapse Analytics Analytics Platform System (PDW)

Defines a date that is combined with a time of day with fractional seconds that is based on a 24-hour clock.

Avoid using datetime for new work. Instead, use the time, date, datetime2, and datetimeoffset data types. These types align with the SQL Standard, and are more portable. time, datetime2 and datetimeoffset provide more seconds precision. datetimeoffset provides time zone support for globally deployed applications.

Description

Property Value
Syntax DATETIME
Usage DECLARE @MyDatetime DATETIME;
CREATE TABLE Table1 (Column1 DATETIME);
Default string literal formats (used for down-level client) Not applicable
Date range 1753-01-01 (January 1, 1753) through 9999-12-31 (December 31, 9999)
Time range 00:00:00 through 23:59:59.997
Time zone offset range None
Element ranges yyyy is four digits from 1753 through 9999 that represent a year.

MM is two digits, ranging from 01 to 12, that represent a month in the specified year.

dd is two digits, ranging from 01 to 31 depending on the month, which represent a day of the specified month.

HH is two digits, ranging from 00 to 23, that represent the hour.

mm is two digits, ranging from 00 to 59, that represent the minute.

ss is two digits, ranging from 00 to 59, that represent the second.

n* is zero to three digits, ranging from 0 to 999, that represent the fractional seconds.
Character length 19 positions minimum to 23 maximum
Storage size 8 bytes
Accuracy Rounded to increments of .000, .003, or .007 seconds
Default value 1900-01-01 00:00:00
Calendar Gregorian (includes the complete range of years)
User-defined fractional second precision No
Time zone offset aware and preservation No
Daylight saving aware No

Supported string literal formats for datetime

The following tables list the supported string literal formats for datetime. Except for ODBC, datetime string literals are in single quotation marks ('), for example, 'string_literaL'. If the environment isn't us_english, the string literals should be in Unicode format N'string_literaL'.

Numeric format

You can specify date data with a numeric month specified. For example, 5/20/97 represents the twentieth day of May 1997. When you use numeric date format, specify the month, day, and year in a string that uses slash marks (/), hyphens (-), or periods (.) as separators. This string must appear in the following form:

<number separator number separator number [time] [time]>

When the language is set to us_english, the default order for the date is mdy (month, day, year). You can change the date order by using the SET DATEFORMAT statement.

The setting for SET DATEFORMAT determines how date values are interpreted. If the order doesn't match the setting, the values aren't interpreted as dates. Out-of-order dates might be misinterpreted as out of range or with wrong values. For example, 12/10/08 can be interpreted as one of six dates, depending on the DATEFORMAT setting. A four-part year is interpreted as the year.

Date format Order
[0]4/15/[19]96 mdy
[0]4-15-[19]96 mdy
[0]4.15.[19]96 mdy
[0]4/[19]96/15 myd
15/[0]4/[19]96 dmy
15/[19]96/[0]4 dym
[19]96/15/[0]4 ydm
[19]96/[0]4/15 ymd
Time format
14:30
14:30[:20:997]
14:30[:20.9]
4am
4 PM

Alphabetical format

You can specify date data with a month specified as the full month name. For example, April, or the month abbreviation of Apr, specified in the current language. Commas are optional and capitalization is ignored.

Here are some guidelines for using alphabetical date formats:

  • Enclose the date and time data in single quotation marks ('). For languages other than English, use N''.

  • Characters that are enclosed in brackets are optional.

  • If you specify only the last two digits of the year, values less than the last two digits of the value of the two digit year cutoff configuration option are in the same century as the cutoff year. Values greater than or equal to the value of this option are in the century that comes before the cutoff year. For example, if two digit year cutoff is 2050 (default), 25 is interpreted as 2025 and 50 is interpreted as 1950. To avoid ambiguity, use four-digit years.

  • If the day is missing, the first day of the month is supplied.

  • The SET DATEFORMAT session setting isn't applied when you specify the month in alphabetical form.

Alphabetical
Apr[il] [15][,] 1996
Apr[il] 15[,] [19]96
Apr[il] 1996 [15]
[15] Apr[il][,] 1996
15 Apr[il][,][19]96
15 [19]96 apr[il]
[15] 1996 apr[il]
1996 APR[IL] [15]
1996 [15] APR[IL]

ISO 8601 format

To use the ISO 8601 format, you must specify each element in the format, including the T, the colons (:), and the period (.) that are shown in the format.

The brackets indicate that the fraction of second component is optional. The time component is specified in the 24-hour format. The T indicates the start of the time part of the datetime value.

The advantage in using the ISO 8601 format is that it's an international standard with unambiguous specification. Also, this format isn't affected by the SET DATEFORMAT or SET LANGUAGE setting.

Examples:

  • 2004-05-23T14:25:10
  • 2004-05-23T14:25:10.487
ISO 8601
yyyy-MM-ddTHH:mm:ss[.mmm]
yyyyMMdd[ HH:mm:ss[.mmm]]

Unseparated format

This format is similar to the ISO 8601 format, except it contains no date separators.

Unseparated
yyyyMMdd HH:mm:ss[.mmm]

ODBC format

The ODBC API defines escape sequences to represent date and time values, which ODBC calls timestamp data. This ODBC timestamp format is also supported by the OLE DB language definition (DBGUID-SQL) supported by the Microsoft OLE DB provider for SQL Server. Applications that use the ADO, OLE DB, and ODBC-based APIs can use this ODBC timestamp format to represent dates and times.

ODBC timestamp escape sequences are of the format: { <literal_type> '<constant_value>' }:

  • <literal_type> specifies the type of the escape sequence. Timestamps have three <literal_type> specifiers:

    • d = date only
    • t = time only
    • ts = timestamp (time + date)

  • <constant_value> is the value of the escape sequence. <constant_value> must follow these formats for each <literal_type>:

    • d: yyyy-MM-dd
    • t: hh:mm:ss[.fff]
    • ts: yyyy-MM-dd HH:mm:ss[.fff]
ODBC
{ ts '1998-05-02 01:23:56.123' }
{ d '1990-10-02' }
{ t '13:33:41' }

Rounding of datetime fractional second precision

datetime values are rounded to increments of .000, .003, or .007 seconds, as shown in the following example.

SELECT '01/01/2024 23:59:59.999' AS [User-specified value],
    CAST('01/01/2024 23:59:59.999' AS DATETIME) AS [System stored value]
UNION SELECT '01/01/2024 23:59:59.998', CAST('01/01/2024 23:59:59.998' AS DATETIME)
UNION SELECT '01/01/2024 23:59:59.997', CAST('01/01/2024 23:59:59.997' AS DATETIME)
UNION SELECT '01/01/2024 23:59:59.996', CAST('01/01/2024 23:59:59.996' AS DATETIME)
UNION SELECT '01/01/2024 23:59:59.995', CAST('01/01/2024 23:59:59.995' AS DATETIME)
UNION SELECT '01/01/2024 23:59:59.994', CAST('01/01/2024 23:59:59.994' AS DATETIME)
UNION SELECT '01/01/2024 23:59:59.993', CAST('01/01/2024 23:59:59.993' AS DATETIME)
UNION SELECT '01/01/2024 23:59:59.992', CAST('01/01/2024 23:59:59.992' AS DATETIME)
UNION SELECT '01/01/2024 23:59:59.991', CAST('01/01/2024 23:59:59.991' AS DATETIME)
UNION SELECT '01/01/2024 23:59:59.990', CAST('01/01/2024 23:59:59.990' AS DATETIME);

Here's the result set.

User-specified value System stored value
01/01/2024 23:59:59.999 2024-01-02 00:00:00.000
01/01/2024 23:59:59.998
01/01/2024 23:59:59.997
01/01/2024 23:59:59.996
01/01/2024 23:59:59.995		 2024-01-01 23:59:59.997
01/01/2024 23:59:59.994
01/01/2024 23:59:59.993
01/01/2024 23:59:59.992		 2024-01-01 23:59:59.993
01/01/2024 23:59:59.991
01/01/2024 23:59:59.990		 2024-01-01 23:59:59.990

ANSI and ISO 8601 compliance

datetime isn't ANSI or ISO 8601 compliant.

Convert date and time data

When you convert to date and time data types, the Database Engine rejects all values it can't recognize as dates or times. For information about using the CAST and CONVERT functions with date and time data, see CAST and CONVERT.

Convert other date and time types to the datetime data type

This section describes what occurs when other date and time data types are converted to the datetime data type.

When the conversion is from date, the year, month, and day are copied. The time component is set to 00:00:00.000. The following code shows the results of converting a DATE value to a DATETIME value.

DECLARE @date DATE = '12-21-16';
DECLARE @datetime DATETIME = @date;

SELECT @datetime AS '@datetime', @date AS '@date';

Here's the result set.

@datetime                @date
------------------------ -----------
2016-12-21 00:00:00.000  2016-12-21

The previous example uses a region specific date format (MM-DD-YY).

DECLARE @date DATE = '12-21-16';

You should update the example to match the format for your region.

You can also complete the example with the ISO 8601 compliant date format (yyyy-MM-dd). For example:

DECLARE @date DATE = '2016-12-21';
DECLARE @datetime DATETIME = @date;

SELECT @datetime AS '@datetime', @date AS '@date';

When the conversion is from time(n), the time component is copied, and the date component is set to 1900-01-01. When the fractional precision of the time(n) value is greater than three digits, the value is truncated to fit. The following example shows the results of converting a TIME(4) value to a DATETIME value.

DECLARE @time TIME(4) = '12:10:05.1237';
DECLARE @datetime DATETIME = @time;

SELECT @datetime AS '@datetime', @time AS '@time';

Here's the result set.

@datetime                @time
------------------------ --------------
1900-01-01 12:10:05.123  12:10:05.1237

When the conversion is from smalldatetime, the hours and minutes are copied. The seconds and fractional seconds are set to 0. The following code shows the results of converting a SMALLDATETIME value to a DATETIME value.

DECLARE @smalldatetime SMALLDATETIME = '12-01-16 12:32';
DECLARE @datetime DATETIME = @smalldatetime;

SELECT @datetime AS '@datetime', @smalldatetime AS '@smalldatetime';

Here's the result set.

@datetime                @smalldatetime
------------------------ --------------------
2016-12-01 12:32:00.000  2016-12-01 12:32:00

When the conversion is from datetimeoffset(n), the date and time components are copied. The time zone is truncated. When the fractional precision of the datetimeoffset(n) value is greater than three digits, the value is truncated. The following example shows the results of converting a DATETIMEOFFSET(4) value to a DATETIME value.

DECLARE @datetimeoffset DATETIMEOFFSET(4) = '1968-10-23 12:45:37.1234 +10:0';
DECLARE @datetime DATETIME = @datetimeoffset;

SELECT @datetime AS '@datetime', @datetimeoffset AS '@datetimeoffset';

Here's the result set.

@datetime                @datetimeoffset
------------------------ -------------------------------
1968-10-23 12:45:37.123  1968-10-23 12:45:37.1237 +10:0

When the conversion is from datetime2(n), the date and time are copied. When the fractional precision of the datetime2(n) value is greater than three digits, the value is truncated. The following example shows the results of converting a DATETIME2(4) value to a DATETIME value.

DECLARE @datetime2 DATETIME2(4) = '1968-10-23 12:45:37.1237';
DECLARE @datetime DATETIME = @datetime2;

SELECT @datetime AS '@datetime', @datetime2 AS '@datetime2';

Here's the result set.

@datetime                @datetime2
------------------------ -------------------------
1968-10-23 12:45:37.123  1968-10-23 12:45:37.1237

Examples

The following example compares the results of casting a string to each date and time data type.

SELECT CAST('2024-05-08 12:35:29.1234567 +12:15' AS TIME(7)) AS 'time',
    CAST('2024-05-08 12:35:29.1234567 +12:15' AS DATE) AS 'date',
    CAST('2024-05-08 12:35:29.123' AS SMALLDATETIME) AS 'smalldatetime',
    CAST('2024-05-08 12:35:29.123' AS DATETIME) AS 'datetime',
    CAST('2024-05-08 12:35:29.1234567 +12:15' AS DATETIME2(7)) AS 'datetime2',
    CAST('2024-05-08 12:35:29.1234567 +12:15' AS DATETIMEOFFSET(7)) AS 'datetimeoffset';

Here's the result set.

Data type Output
time 12:35:29.1234567
date 2024-05-08
smalldatetime 2024-05-08 12:35:00
datetime 2024-05-08 12:35:29.123
datetime2 2024-05-08 12:35:29.1234567
datetimeoffset 2024-05-08 12:35:29.1234567 +12:15

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