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SQL Server FAQ - Subtracting a DATETIME Value from Another DATETIME Value

By: FYIcenter.com

(Continued from previous topic...)

Can a DATETIME Value Be Subtracted from Another DATETIME Value?

Can a datetime value be subtracted from another datetime value? The answer is yes. The subtract operation can be performed by the subtract operator (-) as:

• datetime1 - datetime2: Returning a DATETIME value calculated as CONVERT(DATETIME, CONVERT(NUMERIC(18,9),datetime1) - CONVERT(NUMERIC(18,9),datetime2)).

The tutorial exercise below shows you some good examples:

DECLARE @birth_date DATETIME;
DECLARE @today_date DATETIME;
SET @birth_date = '2000-02-29 16:00:00.000';
SET @today_date = '2007-05-19 22:00:00.000';
SELECT @today_date - @birth_date;
GO
1907-03-22 06:00:00.000

DECLARE @birth_date DATETIME;
DECLARE @today_date DATETIME;
DECLARE @age NUMERIC(9,2);
SET @birth_date = '2000-02-29 16:00:00.000';
SET @today_date = '2007-05-19 22:00:00.000';
SET @age = CONVERT(NUMERIC(9,2), @today_date - @birth_date);
SELECT @age;
GO
2636.25

(Continued on next topic...)

1. How To Add or Remove Days on Date and Time Values?
2. Can Date and Time Values Be Converted into Integers?
3. Can Integers Be Converted into Date and Time Values?
4. Are DATETIME and NUMERIC Values Convertible?
5. Can a DATETIME Value Be Subtracted from Another DATETIME Value?
6. What Are the Date and Time Functions Supported by SQL Server 2005?
7. How To Increment or Decrement Parts of DATETIME Values?
8. How To Use DATEADD() Function?
9. How To Calculate DATETIME Value Differences Using the DATEDIFF() Function?
10. How To Calculate Age in Days, Hours and Minutes?
11. How To Get Month and Weekday Names from DATETIME Values?
12. How To Get Parts of DATETIME Values as Integers?
13. How To Get Year, Month and Day Out of DATETIME Values?
14. What Is the Difference Between GETDATE() and GETUTCDATE()?
15. How To Format Time Zone in +/-hh:mm Format?
16. How To Format DATETIME Values to Strings with the CONVERT() Function?
17. How To Truncate DATETIME Values to Dates without Time?
18. How To Set Different Parts of a DATETIME Value?