mysql name(이름) masking

DELIMITER //
CREATE DEFINER=`mcouponbo`@`%` FUNCTION `getMaskName`(`v_code` varchar(10)) RETURNS varchar(50) CHARSET utf8
BEGIN
declare return_value varchar(50);

SELECT
CASE CHAR_LENGTH(v_code)
WHEN 0 THEN ''
WHEN 1 THEN '*'
WHEN 2 THEN CONCAT('*', SUBSTRING(v_code, 2, 1))
ELSE CONCAT(SUBSTRING(v_code, 1, 1), REPEAT('*', CHAR_LENGTH(v_code) - 2), SUBSTRING(v_code, CHAR_LENGTH(v_code), 1))
END INTO return_value;

RETURN return_value;
END//
DELIMITER ;