假设您的表test包含以下数据：

  select id, email
    from test;

ID                     EMAIL                
---------------------- -------------------- 
1                      aaa                  
2                      bbb                  
3                      ccc                  
4                      bbb                  
5                      ddd                  
6                      eee                  
7                      aaa                  
8                      aaa                  
9                      eee

因此，我们需要找到所有重复的电子邮件并删除所有重复的电子邮件，但是最新的ID。
在这种情况下，aaa，bbb和eee重复，所以我们要删除ID为1，7,2和6。

为此，首先我们需要查找所有重复的电子邮件：

      select email 
        from test
       group by email
      having count(*) > 1;

EMAIL                
-------------------- 
aaa                  
bbb                  
eee

然后，从该数据集中，我们需要为这些重复的电子邮件中的每一封找到最新的ID：

  select max(id) as lastId, email
    from test
   where email in (
              select email 
                from test
               group by email
              having count(*) > 1
       )
   group by email;

LASTID                 EMAIL                
---------------------- -------------------- 
8                      aaa                  
4                      bbb                  
9                      eee

最后，我们现在可以删除所有ID小于LASTID的电子邮件。因此解决方案是：

delete test
  from test
 inner join (
  select max(id) as lastId, email
    from test
   where email in (
              select email 
                from test
               group by email
              having count(*) > 1
       )
   group by email
) duplic on duplic.email = test.email
 where test.id < duplic.lastId;

我现在没有在这台机器上安装mySql，但是应该可以

更新资料

上面的删除有效，但是我发现了一个更优化的版本：

 delete test
   from test
  inner join (
     select max(id) as lastId, email
       from test
      group by email
     having count(*) > 1) duplic on duplic.email = test.email
  where test.id < duplic.lastId;

您会看到它删除了最旧的重复项，即1、7、2、6：

select * from test;
+----+-------+
| id | email |
+----+-------+
|  3 | ccc   |
|  4 | bbb   |
|  5 | ddd   |
|  8 | aaa   |
|  9 | eee   |
+----+-------+

另一个版本是Rene Limon删除的内容

delete from test
 where id not in (
    select max(id)
      from test
     group by email)