About query oracle tablespace

SELECT UPPER(F.TABLESPACE_NAME) "±í¿Õ¼äÃû",
       D.TOT_GROOTTE_MB "±í¿Õ¼ä´óС(M)",
       D.TOT_GROOTTE_MB - F.TOTAL_BYTES "ÒÑʹÓÿռä(M)",
       TO_CHAR(ROUND((D.TOT_GROOTTE_MB - F.TOTAL_BYTES) / D.TOT_GROOTTE_MB * 100,2),'990.99') "ʹÓñÈ",
       F.TOTAL_BYTES "¿ÕÏпռä(M)",
       F.MAX_BYTES "×î´ó¿é(M)"
  from (SELECT TABLESPACE_NAME,
               ROUND(SUM(BYTES) / (1024 * 1024), 2) TOTAL_BYTES,
               ROUND(MAX(BYTES) / (1024 * 1024), 2) MAX_BYTES
          from SYS.DBA_FREE_SPACE
         GROUP BY TABLESPACE_NAME) F,
       (SELECT DD.TABLESPACE_NAME,
               ROUND(SUM(DD.BYTES) / (1024 * 1024), 2) TOT_GROOTTE_MB
          from SYS.DBA_DATA_FILES DD
         GROUP BY DD.TABLESPACE_NAME) D
 WHERE D.TABLESPACE_NAME = F.TABLESPACE_NAME
 ORDER BY 4 DESC