1、先查有没有循环的同义词：
select * from dba_synonyms where
table_owner='test' and synonym_name
<>table_name;没有记录
2、再查同义词没有对象的数据库对象：
select * from dba_synonyms where
table_owner='test'
and sysnonym_name in(select a.synonym_name from dba_synonyms a
where a.table_owner='test'
minus
select object_name from user_objects
)
3、把查询出来的结果进行查询表
select * from DRILL_PRESON
如果该同义词没有对应的对象，就会报ora_01775的错误
4、删除这个同义词：
drop public synonym DRILL_PRESON