Is most simple:
DECLARE @Birthday date = '1994/12/10'
SELECT (CAST(CONVERT(VARCHAR(8), GETDATE(), 112) AS INT) - CAST(CONVERT(VARCHAR(8), @Birthday, 112) AS INT)) / 10000 AS Age
I've not checked some of the possibilities nor have I checked it for performance but THAT IS mighty interesting especially for how it correctly determines ages when a Leap Day is involved.
Thanks, this solution is ideal for BI, since the IDs of the dates are numbers of the same (Example "2017/05/05" has ID 20170505), so that the IDs would be used directly. This method is based on mathematics and bit-shift (in this case decimal shift)