196. 删除重复的电子邮箱

196. 删除重复的电子邮箱

利用 email 字段自连接

delete p1 from person as p1, person as p2
where p1.email = p2.email -- 自连接
and p1.id > p2.id; -- 要求删除 id 大的记录，因为是 delete p1，所以条件是 p1.id > p2.id