如何查看索引或table所佔用的實際空間

select segment_name "对象名称", round(bytes/1024/1024,2)||'M' "对象大小"
from dba_segments;

select *
from dba_segments t where t.tablespace_name='OPENTKT_DAT' and t.segment_type='INDEX';

select segment_name "对象名称", round(bytes/1024/1024,2)||'M' "对象大小"
from dba_segments t where t.tablespace_name='OPENTKT_DAT' and t.segment_type='INDEX' and t.segment_name='IX_DHJAIRELINE_02';

segment_name为 索引 或者 表的名称