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