oracle給使用者分配特定使用者下特定表的只讀許可權

以下是測試過程，測試環境oracle 11.2.0.3 linux平臺：

模擬將HR使用者下的employees表的只讀許可權非配給test_ycr
建立使用者：
SQL> create user test_ycr identified by oracle;
SQL> grant create session to test_ycr;
Grant succeeded.
此時使用者無法選擇employee表：
SQL> conn test_ycr/oracle;
Connected.
SQL> select employee_id from hr.employees;
select employee_id from hr.employees
                           *
ERROR at line 1:
ORA-00942: table or view does not exist
給test_ycr使用者賦予employees表的只讀許可權後實現只讀：
SQL> conn / as sysdba
Connected.
SQL> grant select on hr.employees to test_ycr;
Grant succeeded.
SQL> conn test_ycr/oracle
Connected.
SQL> select employee_id from hr.employees where employee_id=206;
EMPLOYEE_ID
-----------
        206
但是無法修改：
SQL> update hr.employees set employee_id=333 where employee_id=206;
update hr.employees set employee_id=333 where employee_id=206
          *
ERROR at line 1:
ORA-01031: insufficient privileges