SQL Server GetAge Function

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

CREATE FUNCTION [dbo].[GetAge] (@DOB DATETIME, @Today DATETIME)
RETURNS INT
AS
BEGIN
     -- declare variables
     DECLARE @Age INT

     -- set defaults
     SET @Age = Year(@Today) - Year(@DOB)

     -- if it is a previous month subtract one off the age
     IF Month(@Today) < Month(@DOB)
     BEGIN
          SET @Age = @Age -1
     END

     -- if it is the current month but a previous day subtract one off the age
     IF Month(@Today) = Month(@DOB) AND Day(@Today) < Day(@DOB)
     BEGIN
          SET @Age = @Age - 1
     END 

     -- return value
     RETURN @Age
END

Usage

-- declare variables
DECLARE @Today AS DATETIME

-- set default values
SET @Today = GetDate()

-- get data
SELECT   ID,
             DOB,
             'Age' = dbo.GetAge(DOB, @Today)
FROM     MyTable