cfox 61877 (1/23/2015)

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I find this works better than a scalar function...

CREATE FUNCTION dbo.AgeInYears

(

@BirthDate DATETIME2,

@AsOfDate DATETIME2

)

RETURNS TABLE

AS

RETURN

(

SELECT DATEDIFF(YEAR , @BirthDate , @AsOfDate) -

CASE WHEN DATEPART(DY, @AsOfDate) < DATEPART(DY, @BirthDate) THEN 1

ELSE 0

END AS Age

);

Then a simple CROSS APPLY in the query...

SELECT I.Name, I.Birthdate, A.Age

FROM Individual AS I

CROSS APPLY AgeInYears(I.Birthdate, CURRENT_TIMESTAMP) AS A

WHERE A.Age >= 18;