SQL> conn / as sysdba
Connected.
SQL> create user query identified by query;

User created.

SQL> grant connect,resource to query;

Grant succeeded.

SQL> conn u01/u01
Connected.
SQL> select 'GRANT SELECT ON ' || table_name || ' to query;'  from user_tables;    --通过查询语句快速生成授权u01下所有表给scott用户的语句

'GRANTSELECTON'||TABLE_NAME||'TOQUERY;'
--------------------------------------------------------
GRANT SELECT ON T2 to query;
GRANT SELECT ON T to query;
GRANT SELECT ON T_TARGET to query;
GRANT SELECT ON EMPLOYEES to query;
GRANT SELECT ON AA to query;
GRANT SELECT ON T_PART to query;
GRANT SELECT ON MOBILEMESSAGE to query;
GRANT SELECT ON T1 to query;
GRANT SELECT ON T_PART_ARCH to query;

执行上面的授权语句

创建dblink（通过该dblink在nba实例中可以查看orcl实例中query用户所有表以及上面u01用户授权给query用户的所有表）
SQL> create public database link nba_to_orcl connect to query identified by query using 'orcl';

测试dblink
SQL> select * from QUERY.T1@NBA_TO_ORCL;

    ID NAME
---------- ------------------------------------------------------------
     1 aa

SQL> select * from u01.test3@NBA_TO_ORCL;

    ID NAME
---------- ------------------------------
     3 cat