本题来自力扣182. 查找重复的电子邮箱 。难度：简单

错误解法❌：

select Email from Person group by  Email where count(Email)>1;

因为：sql语句的执行过程是：from-->where-->group by -->having --- >order by --> select

聚合函数count是根据结果进行聚合的，而where语句很早就被执行了此时表还没被分组

正确解法✔：

select Email from Person group by  Email having  count(Email)>1;