dba_tablses tablespace_name为空 dba_tablses tablespace_name null DBA_PART_TABLES,DBA_TABLES

Partitioned tables, global temporary tables and external tables.

Partitioned table ,Temporary tables and IOT tables do not have tablespace entries for
starters.

key words:

DBA_TABLES,DBA_PART_TABLES

You may have partitioned tables, index organized tables (IOTs), or global temporary tables (GTTs) defined so that you can see them.

select
	table_name,
	iot_type,
	partitioned,
	temporary
from
	all_tables
where
	tablespace_name is null
order by
	iot_type, partitioned desc, temporary
/
TABLE_NAME           IOT_TYPE     PAR T
-------------------- ------------ --- -
PT_IOT               IOT          YES N
EMPIOT               IOT          NO  N
PT_RL                             YES N
GTT1                              NO  Y

refer:http://forums.oracle.com/forums/message.jspa?messageID=2017310