with t as (select seg.segment_name , bytes/1024/1024 as sgesize from dba_segments seg  order by sgesize desc ),
 t1 as (
 select rownum as rn , t.* from t ) 
 select * from t1 where t1.rn <10;

如果查詢的segment 是clob等類型，需進一步確定其表名及字段名

SELECT B.TABLE_NAME,  B.COLUMN_NAME,  A.SEGMENT_NAME,
       a.SEGMENT_TYPE,  ROUND(SUM(A.BYTES / 1024 / 1024 / 1024), 2) GB
  FROM DBA_SEGMENTS A  LEFT JOIN DBA_LOBS B   ON A.OWNER = B.OWNER
   AND A.SEGMENT_NAME = B.SEGMENT_NAME
 WHERE B.SEGMENT_NAME = 'SYS_LOB00000********17$$'
 GROUP BY B.TABLE_NAME, B.COLUMN_NAME, A.SEGMENT_NAME,a.SEGMENT_TYPE;