Try this UDF:

-----------------------------------------------------------------------------------

SET QUOTED_IDENTIFIER ON

GO

SET ANSI_NULLS ON

GO

if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[udf_AgeFromDOB]') and xtype in (N'FN', N'IF', N'TF'))

drop function [dbo].[udf_AgeFromDOB]

GO

CREATE FUNCTION [dbo].[udf_AgeFromDOB]

(

@DOB as...