SQL
如果用户的等级不够建立public同义词，可以在system下授权：
grant create any synonym to scott;
grant create public synonym to scott;
取消授权：
revoke create any synoym from scott;
revoke create public synoym from scott;
取消同义词：
drop public synonym abc;
授权取消同义词：
grant dorp public synonym to scott;
取消授权：
revoke drop public synonym to scott;