SQL> conn / as sysdba
已连接。SQL> grant create public synonym to scott;授权成功。SQL> grant create any synonym to scott;授权成功。SQL> conn scott/tiger
已连接。SQL> create public synonym mydept for dept;    ##创建公有同义词，其它用户也可以访问同义词已创建。SQL> create  synonym mydept for dept;　　　　　　##创建私有同义词，只有Scott才可以访问，与公共同义词同名，并没有报错

同义词已创建。

SQL> drop public synonym mydept;同义词已删除。SQL> select * from mydept;   ##删除共有同义词，私有的还在DEPTNO DNAME      LOC
---------- -------------- -------------10 ACCOUNTING      NEW YORK20 RESEARCH      DALLAS30 SALES      CHICAGO40 OPERATIONS      BOSTONSQL> drop synonym mydept;
同义词已删除。
SQL> select * from mydept;
select * from mydept*
第 1 行出现错误:
ORA-00942: 表或视图不存在

SQL> select * from user_synonyms;SYNONYM_NAME               TABLE_OWNER              TABLE_NAME
------------------------------ ------------------------------ ------------------------------
DB_LINK
------------------------------------------------------------------------------------------------------------------------
MYDEPT                   SCOTT                  DEPTSQL> conn / as sysdba
已连接。SQL> SELECT synonym_name,table_owner,table_name FROM dba_synonyms  WHERE table_name = 'DEPT';SYNONYM_NAME               TABLE_OWNER              TABLE_NAME
------------------------------ ------------------------------ ------------------------------
MYDEPT                   SCOTT                      DEPT
MYDEPT                   SCOTT                       DEPT