如何删除SQL中的重复行？

Question

我的表名是emails。

我的表格结构如下：

我想删除所有重复的电子邮件。我试过这个问题：

DELETE FROM emails WHERE email NOT IN (SELECT MIN(email)
    FROM emails GROUP BY email) 

但没有结果。有人可以帮我这个吗？

Answer 1

您要查找的查询将使用id，而不是email：

DELETE FROM emails
    WHERE id NOT IN (SELECT MIN(id) FROM emails GROUP BY email) ;

编辑：

您正在使用MySQL。您可以使用子查询黑客来解决这个问题：

DELETE FROM emails
    WHERE id NOT IN (select minid from (SELECT MIN(id) as minid FROM emails GROUP BY email) e) ;

或者，您可以使用join：

delete e
    from emails e left outer join
         (select min(id) as minid
          from emails
          group by email
         ) em
         on e.id = e.minid
    where em.id is null;

Answer 2

试试这个

- 创建临时表

create table IDsToRemove (ID Int)
INSERT INTO IDStoRemove
     SELECT MIN(id) _
            FROM emails GROUP BY email 


      DELETE FROM emails WHERE id NOT IN (SELECT id from IDStoRemove) 

我不知道确切的mySQL语法，但应该给你一个想法

Answer 3

也许你（或某人）想要删除独特的记录，我会在这里留下这个被盗的答案[0]。

DELETE Emails 
FROM Emails
  LEFT OUTER JOIN (
    SELECT MIN(id) as id, email, pwd
    FROM Emails
    GROUP BY email, pwd
  ) as KeepRows ON
  Emails.id = KeepRows.id
WHERE
  KeepRows.id IS NULL

0。How can I remove duplicate rows?