//查看当前用户的缺省表空间 
sql>select username,default_tablespace from user_users;
//查询表空间
select * from sys.dba_tablespaces;
//修改用户的表空间
alter user test1 default tablespace user_tbs
//删除表空间
 DROP TABLESPACE tablespacename INCLUDING CONTENTS AND DATAFILES CASCADE CONSTRAINTS;