Get index of occurrence any characters from string in SQL Server

Return index of the first occurrence in the string of any character in a specified string characters.

CREATE FUNCTION [dbo].[IndexOfAny] (

      @Chars VARCHAR(100),

      @Delimiter VARCHAR(10),

      @String VARCHAR(MAX)

)

RETURNS INT

AS

BEGIN

      DECLARE @Index AS INT

      DECLARE @Length AS INT

      DECLARE @Value AS VARCHAR(100)

      SET @Length = 0

      WHILE @Length >= 0

      BEGIN

            SET @Length = CHARINDEX(@Delimiter, @Chars) - 1

            IF @Length > 0

            BEGIN

                  SET @Value = LEFT(@Chars, @Length)

                  SET @Chars = STUFF(@Chars, 1, @Length + LEN(@Delimiter), '')

            END

            ELSE

                  SET @Value = @Chars

            SET @Index = CASE

                        WHEN CHARINDEX(@Value, @String) <> 0

                              AND (

                                    @Index IS NULL

                                    OR CHARINDEX(@Value, @String) < @Index

                                    )

                              THEN CHARINDEX(@Value, @String)

                        ELSE @Index

                        END

      END

      RETURN ISNULL(@Index, 0)

END

Example:

SELECT [dbo].[IndexOfAny]('A,B,C', ',', 'xxxBxxxAxxxCxxx')

Output: 4