DATEDIFF (Transact-SQL)

Returns the count (signed integer) of the specified datepart boundaries crossed between the specified startdate and enddate.

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

Transact-SQL Syntax Conventions

Syntax

DATEDIFF ( datepart , startdate , enddate )

Arguments

• datepart
  Is the part of startdate and enddate that specifies the type of boundary crossed. 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
  hour	hh
  minute	mi, n
  second	ss, s
  millisecond	ms
  microsecond	mcs
  nanosecond	ns

• startdate
  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. startdate is subtracted from enddate.

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

• enddate
  See startdate.

Return Type

int

Return Value

Each datepart and its abbreviations return the same value.

If the return value is out of range for int (-2,147,483,648 to +2,147,483,647), an error is returned. For millisecond, the maximum difference between startdate and enddate is 24 days, 20 hours, 31 minutes and 23.647 seconds. For second, the maximum difference is 68 years.

If startdate and enddate are both assigned only a time value and the datepart is not a time datepart, 0 is returned.

A time zone offset component of startdate or endate is not used in calculating the return value.

Because smalldatetime is accurate only to the minute, when a smalldatetime value is used for startdate or enddate, seconds and milliseconds are always set to 0 in the return value.

If only a time value is assigned to a variable of a date data type, the value of the missing date part is set to the default value: 1900-01-01. If only a date value is assigned to a variable of a time or date data type, the value of the missing time part is set to the default value: 00:00:00. If either startdate or enddate have only a time part and the other only a date part, the missing time and date parts are set to the default values.

If startdate and enddate are of different date data types and one has more time parts or fractional seconds precision than the other, the missing parts of the other are set to 0.

datepart Boundaries

The following statements have the same startdate and the same endate. Those dates are adjacent and differ in time by .0000001 second. The difference between the startdate and endate in each statement crosses one calendar or time boundary of its datepart. Each statement returns 1. If different years are used for this example and if both startdate and endate are in the same calendar week, the return value for week would be 0.

SELECT DATEDIFF(year, '2005-12-31 23:59:59.9999999'

, '2006-01-01 00:00:00.0000000');

SELECT DATEDIFF(quarter, '2005-12-31 23:59:59.9999999'

, '2006-01-01 00:00:00.0000000');

SELECT DATEDIFF(month, '2005-12-31 23:59:59.9999999'

, '2006-01-01 00:00:00.0000000');

SELECT DATEDIFF(dayofyear, '2005-12-31 23:59:59.9999999'

, '2006-01-01 00:00:00.0000000');

SELECT DATEDIFF(day, '2005-12-31 23:59:59.9999999'

, '2006-01-01 00:00:00.0000000');

SELECT DATEDIFF(week, '2005-12-31 23:59:59.9999999'

, '2006-01-01 00:00:00.0000000');

SELECT DATEDIFF(hour, '2005-12-31 23:59:59.9999999'

, '2006-01-01 00:00:00.0000000');

SELECT DATEDIFF(minute, '2005-12-31 23:59:59.9999999'

, '2006-01-01 00:00:00.0000000');

SELECT DATEDIFF(second, '2005-12-31 23:59:59.9999999'

, '2006-01-01 00:00:00.0000000');

SELECT DATEDIFF(millisecond, '2005-12-31 23:59:59.9999999'

, '2006-01-01 00:00:00.0000000');

Remarks

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

DATEDIFF implicitly casts string literals as a datetime2 type. This means that DATEDIFF 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.

Specifying SET DATEFIRST has no effect on DATEDIFF. DATEDIFF always uses Sunday as the first day of the week to ensure the function is deterministic.

Examples

The following examples use different types of expressions as arguments for the startdate and enddate parameters.

A. Specifying columns for startdate and enddate

The following example calculates the number of day boundaries that are crossed between dates in two columns in a table.

CREATE TABLE dbo.Duration
    (
    startDate datetime2
    ,endDate datetime2
    );
INSERT INTO dbo.Duration(startDate,endDate)
    VALUES('2007-05-06 12:10:09','2007-05-07 12:10:09');
SELECT DATEDIFF(day,startDate,endDate) AS 'Duration'
FROM dbo.Duration;
-- Returns: 1

B. Specifying user-defined variables for startdate and enddate

The following example uses user-defined variables as arguments for startdate and enddate.

DECLARE @startdate datetime2 = '2007-05-05 12:10:09.3312722';
DECLARE @enddate datetime2 = '2007-05-04 12:10:09.3312722'; 
SELECT DATEDIFF(day, @startdate, @enddate);

C. Specifying scalar system functions for startdate and enddate

The following example uses scalar system functions as arguments for startdate and enddate.

SELECT DATEDIFF(millisecond, GETDATE(), SYSDATETIME());

D. Specifying scalar subqueries and scalar functions for startdate and enddate

The following example uses scalar subqueries and scalar functions as arguments for startdate and enddate.

USE AdventureWorks2012;
GO
SELECT DATEDIFF(day,(SELECT MIN(OrderDate) FROM Sales.SalesOrderHeader),
    (SELECT MAX(OrderDate) FROM Sales.SalesOrderHeader));

E. Specifying constants for startdate and enddate

The following example uses character constants as arguments for startdate and enddate.

SELECT DATEDIFF(day, '2007-05-07 09:53:01.0376635'
    , '2007-05-08 09:53:01.0376635');

F. Specifying numeric expressions and scalar system functions for enddate

The following example uses a numeric expression, (GETDATE ()+ 1), and scalar system functions, GETDATE and SYSDATETIME, as arguments for enddate.

USE AdventureWorks2012;
GO
SELECT DATEDIFF(day, '2007-05-07 09:53:01.0376635', GETDATE()+ 1) 
    AS NumberOfDays
FROM Sales.SalesOrderHeader;
GO
USE AdventureWorks2012;
GO
SELECT DATEDIFF(day, '2007-05-07 09:53:01.0376635', DATEADD(day,1,SYSDATETIME())) AS NumberOfDays
FROM Sales.SalesOrderHeader;
GO

G. Specifying ranking functions for startdate

The following example uses a ranking function as an argument for startdate.

USE AdventureWorks2012;
GO
SELECT p.FirstName, p.LastName
    ,DATEDIFF(day,ROW_NUMBER() OVER (ORDER BY 
        a.PostalCode),SYSDATETIME()) AS 'Row Number'
FROM Sales.SalesPerson s 
    INNER JOIN Person.Person p 
        ON s.BusinessEntityID = p.BusinessEntityID
    INNER JOIN Person.Address a 
        ON a.AddressID = p.BusinessEntityID
WHERE TerritoryID IS NOT NULL 
    AND SalesYTD <> 0;

H. Specifying an aggregate window function for startdate

The following example uses an aggregate window function as an argument for startdate.

USE AdventureWorks2012;
GO
SELECT soh.SalesOrderID, sod.ProductID, sod.OrderQty,soh.OrderDate
    ,DATEDIFF(day,MIN(soh.OrderDate) 
        OVER(PARTITION BY soh.SalesOrderID),SYSDATETIME() ) AS 'Total'
FROM Sales.SalesOrderDetail sod
    INNER JOIN Sales.SalesOrderHeader soh
        ON sod.SalesOrderID = soh.SalesOrderID
WHERE soh.SalesOrderID IN(43659,58918);
GO

See Also

Reference

CAST and CONVERT (Transact-SQL)