SQL - Remove Special Characters

Removes all special characters from an input string.

USE MIGRATION_DB
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
IF OBJECT_ID (N'dbo.RemoveSpecialChars', N'FN') IS NOT NULL
    DROP FUNCTION dbo.RemoveSpecialChars;
GO
CREATE FUNCTION dbo.RemoveSpecialChars 
( @InputString VARCHAR(max) 
)
RETURNS VARCHAR(8000)  BEGIN    
IF @InputString IS NULL RETURN NULL    

DECLARE @OutputString VARCHAR(max)    
SET @OutputString = ''    
DECLARE @l INT    
SET @l = LEN(@InputString)    
DECLARE @p INT    
SET @p = 1
    WHILE @p <= @l
        BEGIN            
        DECLARE @c INT            
        SET @c = ASCII(SUBSTRING(@InputString, @p, 1))            
        IF @c BETWEEN 48 AND 57
                OR @c BETWEEN 65 AND 90
                OR @c BETWEEN 97 AND 122
                  --OR @c = 32                
                  SET @OutputString = @OutputString + CHAR(@c)            
                  SET @p = @p + 1
        END    IF LEN(@OutputString) = 0  RETURN NULL    
RETURN @OutputString
END
GO