这个MySQL查询总是返回预期的结果吗?

我不确定。但如果您担心,可以对子查询应用限制:

select *
from 
(
  SELECT COUNT(*) AS count, email
  FROM sometable
  GROUP BY email
  ORDER BY count DESC 
)
limit 4

或者,您也可以这样做来查看所有重复的电子邮件地址(可能返回的电子邮件地址多于或少于4个):

  SELECT COUNT(*) AS count, email
    FROM sometable
GROUP BY email
having COUNT(email) > 1
ORDER BY count DESC 

首先,查询不仅返回重复的条目。看第四行,它表示count=1,这意味着它只在表中出现一次。若要列出重复的记录,您需要将查询修改为-

SELECT COUNT(*) AS count, email
FROM sometable
GROUP BY email
HAVING COUNT(*) > 1
ORDER BY count DESC     
LIMIT 4

然后,按照前面提到的顺序,这将始终返回表中最上面的4个重复条目。