generate auto number mysql before insert with unique logic concat with primary key

generate_unique_with_primary_key.sql

DELIMITER $$

DROP TRIGGER IF EXISTS `auto_number`$$
CREATE TRIGGER `auto_number` BEFORE INSERT on users
FOR EACH ROW BEGIN
     SET new.auto_number = CONCAT(new.id, LEFT(UUID(), 8));
END$$

DELIMITER ;

other solution

SET new.auto_number = CONCAT(LAST_INSERT_ID(), LEFT(UUID(), 8));

i have thinking about the pk normaly is auto generate thats mean null .
if your unique number is not null on generate use SET new.auto_number = CONCAT(new.id, LEFT(UUID(), 8));