SQL Function to Remove Alphanumeric Characters

I created a customisation recently for a client which would generate a Vendor ID based on the name, by removing alphanumeric characters. In order to make it as flexible as possible, I created the function to accept a parameter for type which will cause the function to strip different characters:

• A – leaves alpha characters only.
• N – leaves numeric characters only.
• AN – leaves alphanumeric characters.

The second parameter is the string which should have the characters stripped:

IF OBJECT_ID (N'uv_AZRCRV_StripCharacters', N'FN') IS NOT NULL
	DROP FUNCTION uv_AZRCRV_StripCharacters
GO

CREATE FUNCTION uv_AZRCRV_StripCharacters(@Type VARCHAR(100), @String VARCHAR(MAX))
	RETURNS VARCHAR(MAX)
/*
Created by Ian Grieve of azurecurve|Ramblings of a Dynamics GP Consultant (http://www.azurecurve.co.uk)
This code is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0 Int).
*/
BEGIN
	DECLARE @PatIndex VARCHAR(20)
	IF (@Type = 'Alpha' OR @Type = 'A')
		SET @PatIndex = '%[^a-z]%'
	IF (@Type = 'Numeric' OR @Type = 'N')
		SET @PatIndex = '%[^0-9]%'
	IF (@Type = 'AlphaNumeric' OR @Type = 'AN')
		SET @PatIndex = '%[^a-z0-9]%'

	WHILE PATINDEX(@PatIndex, @String) < 0
		SET @String = STUFF(@String, PATINDEX(@PatIndex, @String), 1, '')

	RETURN @String
END

GRANT EXECUTE ON uv_AZRCRV_StripCharacters TO DYNGRP
GO