oracle sql 经过分隔符将字符串转换成行

oracle sql 通过分隔符将字符串转换成行
原始字符串为'aa,bb,cc',分隔符为','

SELECT TRIM(substr(txt,                   instr(txt, ',', 1, LEVEL) + 1,                   instr(txt, ',', 1, LEVEL + 1) - instr(txt, ',', 1, LEVEL) - 1)) AS file_name  FROM (SELECT ',' || 'aa,bb,cc' || ',' txt FROM dual)CONNECT BY LEVEL <=           length('aa,bb,cc') - length(REPLACE('aa,bb,cc', ',', '')) + 1

aabbcc