PL/SQL Split function

SELECT substr(main_string, position_from + 1, position_to - position_from - 1) FROM (SELECT main_string, decode(rownum - 1, 0, 0, instr(main_string, ',', 1, rownum - 1)) position_from, instr(main_string, ',', 1, rownum) position_to FROM (SELECT '111,123,aaabbb,555,' main_string FROM dual) CONNECT BY LEVEL <= length(main_string)) WHERE position_to > 0;