截取文件名:

SELECT SUBSTR('pop.kid.orc.txt', 1, INSTR('pop.kid.orc.txt', '.', -1) - 1) AS FILE_NAME
  FROM DUAL;
截取扩展名:
SELECT SUBSTR('pop.kid.orc.txt',
              INSTR('pop.kid.orc.txt', '.', -1) + 1,
              LENGTH('pop.kid.orc.txt')) AS FILE_NAME
  FROM DUAL;