[japan]

Evo poigrao sam se malo grubom silom u MySQL-u:

DELIMITER $$

DROP FUNCTION IF EXISTS `test`.`simple_path`$$
CREATE FUNCTION `test`.`simple_path` (path char(20)) RETURNS char(20)
BEGIN
	DECLARE counter INT DEFAULT 2;
	DECLARE simple_path char(20) DEFAULT SUBSTR(path, 1, 1);

	WHILE counter <= CHAR_LENGTH(path) DO
		IF SUBSTR(path, counter-1, 1) <> SUBSTR(path, counter, 1) THEN
			set simple_path = CONCAT(simple_path, SUBSTR(path, counter, 1));	
		END IF;
		SET counter = counter + 1;
	END WHILE;
	
	RETURN simple_path;
END$$

DELIMITER ;

select distinct simple_path(concat(step_1, step_2, step_3, step_4, step_5)) from test

Valjda je to to, jedino bi mozda trebalo podesiti ulazni i izlazni tip, ako sam uopste dobro shvatio...