方法一：
select n_code from table1(表名) where n_orgid is not null group by n_code,n_orgid having count(n_orgid)>1
方法二
select * from (select count(n_code) as c from table1(表名) group by n_code,n_orgid) as tt where c>1;
sql 使用group by，having，count函数查询表中某字段相同内容的数据
原文：https://www.cnblogs.com/qingjiawen/p/13202039.html