Oracle 統計資料表空間使用率-經典語句____Oracle

SELECT TABLESPACE_NAME 資料表空間,
       TO_CHAR(ROUND(BYTES / 1024, 2), '99990.00') || '' 實有,
       TO_CHAR(ROUND(FREE / 1024, 2), '99990.00') || 'G' 現有,
       TO_CHAR(ROUND((BYTES - FREE) / 1024, 2), '99990.00') || 'G' 使用,
       TO_CHAR(ROUND(10000 * USED / BYTES) / 100, '99990.00') || '%' 比例
  FROM (SELECT A.TABLESPACE_NAME TABLESPACE_NAME,
               FLOOR(A.BYTES / (1024 * 1024)) BYTES,
               FLOOR(B.FREE / (1024 * 1024)) FREE,
               FLOOR((A.BYTES - B.FREE) / (1024 * 1024)) USED
          FROM (SELECT TABLESPACE_NAME TABLESPACE_NAME, SUM(BYTES) BYTES
                  FROM DBA_DATA_FILES
                 GROUP BY TABLESPACE_NAME) A,
               (SELECT TABLESPACE_NAME TABLESPACE_NAME, SUM(BYTES) FREE
                  FROM DBA_FREE_SPACE
                 GROUP BY TABLESPACE_NAME) B
         WHERE A.TABLESPACE_NAME = B.TABLESPACE_NAME)
  --WHERE TABLESPACE_NAME LIKE 'CDR%'
 ORDER BY FLOOR(10000 * USED / BYTES) DESC;