How to Subtract Dates in SQL Server (Years, Days, Hours, Seconds)

Here's a quick video to show you how to use the DATEDIFF function to subtract dates from each other in SQL Server's transact SQL.

00:00 - Using DATEDIFF
00:30 - Calculating a person's age
01:27 - Subtracting variables

How to use DATEDIFF with column values:

SELECT JobTitle, BirthDate, DATEDIFF(year, BirthDate, GETDATE()) AS 'Rough Age in Years'
FROM [AdventureWorks].[HumanResources].[Employee]

Just be aware that calculating somebody's age is not as straightforward as it looks. DATEDIFF passing in the 'year' parameter just calculates whole years and does not take leap years into account. It's OK as a rough calculation but if you need to precisely calculate a person's age then check out this article:

https://www.wiseowl.co.uk/blog/s216/c...

If you want to calculate differences between past/present and future dates then you can use a query like this:

SELECT DATEDIFF(minute, GETDATE(), '2022-12-31 23:59:59') AS 'Total Minutes Left in Year'

DATEDIFF reference: https://docs.microsoft.com/en-us/sql/...

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