CREATE DEFINER=`root`@`%` FUNCTION `get_count_functional`(str VARCHAR(50) CHARSET utf8mb4 COLLATE 'utf8mb4_0900_ai_ci') RETURNS int
BEGIN

  DECLARE cnt INT(10) DEFAULT 0;
  SELECT count(*) into cnt FROM mytable WHERE concat(n1,n2) = str;
  RETURN (cnt);
	
END