查询某表中存在重复的记录

下面的例子中可以根据一个或者多个fieldfield来判断是否为重复记录。假设某表employees有如下三列：pk, id, email

下面的例子中可以根据一个或者多个fieldfield来判断是否为重复记录。

假设某表employees有如下三列：

pk, id, email

根据id字段来判断重复

select * from employees where id in (select id from employees group by id having count(id) > 1);

根据id和email字段来判断重复

select * from employees e where (e.id, e.email) in (select id, email from employees group by id, email having count(*) > 1);