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DATEDIFF (Transact-SQL)

  • Artikkeli

Returns the number of date and time boundaries crossed between two specified dates.

Topic link iconTransact-SQL Syntax Conventions

Syntax

DATEDIFF ( datepart , startdate , enddate )

Arguments

  • datepart
    Is the parameter that specifies on which part of the date to calculate the difference. The following table lists dateparts and abbreviations recognized by SQL Server 2005. These dateparts and abbreviations cannot be supplied as a user-declared variable.

    Datepart Abbreviations

    year

    yy, yyyy

    quarter

    qq, q

    month

    mm, m

    dayofyear

    dy, y

    day

    dd, d

    week

    wk, ww

    Hour

    hh

    minute

    mi, n

    second

    ss, s

    millisecond

    ms

  • startdate -
    Is the starting date for the calculation. startdate is an expression that returns a datetime or smalldatetime value, or a character string in a date format.

    Because smalldatetime is accurate only to the minute, when a smalldatetime value is used, seconds and milliseconds are always 0.

    If you specify only the last two digits of the year, values less than or equal to 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 the last two digits of the value of this option are in the century that comes before the cutoff year. For example, if the two-digit year cutoff is 2049 (default), 49 is interpreted as 2049 and 2050 is interpreted as 1950. To avoid ambiguity, use four-digit years.

    For more information about how to specify time values, see Time Formats. For more information about how to specify dates, see Date and Time (Transact-SQL).

  • enddate
    Is the ending date for the calculation. enddate is an expression that returns a datetime or smalldatetime value, or a character string in a date format.

Return Types

integer

Remarks

startdate is subtracted from enddate. If startdate is later than enddate, a negative value is returned.

DATEDIFF produces an error if the result is out of range for integer values. For milliseconds, the maximum number is 24 days, 20 hours, 31 minutes and 23.647 seconds. For seconds, the maximum number is 68 years.

The method of counting crossed boundaries such as minutes, seconds, and milliseconds makes the result specified by DATEDIFF consistent across all data types. The result is a signed integer value equal to the number of datepart boundaries crossed between the first and second date. For example, the number of weeks between Sunday, January 4, and Sunday, January 11, is 1.

Examples

The following example determines the difference in days between the current date and the order date for products in the AdventureWorks database.

USE AdventureWorks;
GO
SELECT DATEDIFF(day, OrderDate, GETDATE()) AS NumberOfDays
FROM Sales.SalesOrderHeader;
GO

See Also

Reference

CAST and CONVERT (Transact-SQL)
Data Types (Transact-SQL)
Date and Time Functions (Transact-SQL)

Other Resources

ISO 8601 Format
Alphabetic Date Format
Numeric Date Format
ODBC Datetime Format
Time Formats
Unseparated String Format

Help and Information

Getting SQL Server 2005 Assistance