Transact-SQL Syntax Conventions[!div class=“nextstepaction”] Please help improve SQL Server docs!
This function returns the count (as a signed integer value) of the specified datepart boundaries crossed between the specified startdate and enddate.
See DATEDIFF_BIG (Transact-SQL) for a function that handles larger differences between the startdate and enddate values. See Date and Time Data Types and Functions (Transact-SQL) for an overview of all Transact\-SQL date and time data types and functions.
Transact-SQL Syntax Conventions
datepart
The part of startdate and enddate that specifies the type of boundary crossed. DATEDIFF will not accept user-defined variable equivalents. This table lists all valid datepart arguments.
| 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
An expression that can resolve to one of the following values:
Use four-digit years to avoid ambiguity. See Configure the two digit year cutoff Server Configuration Option for information about two-digit year values.
enddate
See startdate.
int
For a return value out of range for int (-2,147,483,648 to +2,147,483,647), DATEDIFF returns an error. 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, DATEDIFF returns 0.
DATEDIFF does not use a time zone offset component of startdate or enddate to calculate the return value.
Because smalldatetime is accurate only to the minute, seconds and milliseconds are always set to 0 in the return value when startdate or enddate have a smalldatetime value.
If only a time value is assigned to a date data type variable, DATEDIFF sets the value of the missing date part to the default value: 1900-01-01. If only a date value is assigned to a variable of a time or date data type, DATEDIFF sets the value of the missing time part to the default value: 00:00:00. If either startdate or enddate have only a time part and the other only a date part, DATEDIFF sets the missing time and date parts to the default values.
If startdate and enddate have different date data types, and one has more time parts or fractional seconds precision than the other, DATEDIFF sets the missing parts of the other to 0.
The following statements have the same startdate and the same enddate values. Those dates are adjacent and they differ in time by .0000001 second. The difference between the startdate and enddate in each statement crosses one calendar or time boundary of its datepart. Each statement returns 1. If startdate and enddate have different year values but they have the same calendar week values, DATEDIFF will return 0 for datepart week.
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');Use DATEDIFF in the SELECT , 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 operates in a deterministic way.
These examples use different types of expressions as arguments for the startdate and enddate parameters.
This example calculates the number of day boundaries 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 In this example, user-defined variables serve 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); This example uses scalar system functions as arguments for startdate and enddate.
This 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)); This example uses character constants as arguments for startdate and enddate.
This 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 This 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; This 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 These examples use different types of expressions as arguments for the startdate and enddate parameters.
This example calculates the number of day boundaries 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 TOP(1) DATEDIFF(day, startDate, endDate) AS Duration
FROM dbo.Duration;
-- Returns: 1 This example uses scalar subqueries and scalar functions as arguments for startdate and enddate.
-- Uses AdventureWorks
SELECT TOP(1) DATEDIFF(day, (SELECT MIN(HireDate) FROM dbo.DimEmployee),
(SELECT MAX(HireDate) FROM dbo.DimEmployee))
FROM dbo.DimEmployee;
This example uses character constants as arguments for startdate and enddate.
-- Uses AdventureWorks
SELECT TOP(1) DATEDIFF(day,
'2007-05-07 09:53:01.0376635',
'2007-05-08 09:53:01.0376635') FROM DimCustomer; This example uses a ranking function as an argument for startdate.
-- Uses AdventureWorks
SELECT FirstName, LastName,
DATEDIFF(day, ROW_NUMBER() OVER (ORDER BY
DepartmentName), SYSDATETIME()) AS RowNumber
FROM dbo.DimEmployee; This example uses an aggregate window function as an argument for startdate.
-- Uses AdventureWorks
SELECT FirstName, LastName, DepartmentName,
DATEDIFF(year, MAX(HireDate)
OVER (PARTITION BY DepartmentName), SYSDATETIME()) AS SomeValue
FROM dbo.DimEmployee