Find index position of the last occurrence of a specified string within another string SQL Server

SQL function which get last index position of a characters in a string in SQL server

CREATE FUNCTION [dbo].[LastIndexOf] (

      @Chars VARCHAR(10),

      @String VARCHAR(MAX))

RETURNS INT

AS

BEGIN

      IF CHARINDEX(@Chars, @String) = 0

            RETURN 0

      ELSE

            RETURN 2 + DATALENGTH(@String) - CHARINDEX(REVERSE(@Chars), REVERSE(@String)) - DATALENGTH(@Chars)

      RETURN 0

END

Example:

SELECT [dbo].[LastIndexOf]('ab', 'SQLabMySQLabOracleabSQLSERVER')

Output: 19