php – MySQL – 选择性删除重复记录

我有几千个联系人的数据库,并希望删除所有重复的记录.我目前的SQL查询运行良好(在记录中 – 电话,电子邮件,名称1重复).查询删除具有较低ID但最后发生记录的重复项.但在某些情况下,记录的另一个字段已经填写(重要的是标题和名称2).我想要实现的是 mysql检查这些字段是否被填写并仅保留记录了大部分信息的记录.

我的查询

<?php

$del_duplicate_contacts = $mysqli->query("

DELETE  ca
FROM    contacts ca
     LEFT JOIN
  (
 SELECT MAX(id) id,name1,tel,email
            FROM    contacts
            GROUP   BY name1,email
        ) cb ON  ca.id = cb.id AND 
                ca.name1 = cb.name1 AND
                ca.tel = cb.tel AND
                ca.email = cb.email
WHERE   cb.id IS NULL

");

?>

表格示例：

ID   title   name1   name2    tel      email
1            John             01234    1@1.com
2    Mr      John     Smith   01234    1@1.com
3            John             01234    1@1.com

我的查询将删除记录1和2.我想只保留nr 2并删除1和3.
我怎么能做到这一点？有可能吗？或者也许我应该涉及PHP,如果是这样如何？

DELETE c1 FROM contacts c1
JOIN (
    SELECT 
        substring_index(group_concat(id ORDER BY ((title IS NULL OR title ='') AND (name2 IS NULL OR name2 = '')),id DESC),',1) AS id,email
    FROM contacts
    GROUP BY name1,email
) c2
ON c1.name1 = c2.name1 AND c1.tel = c2.tel AND c1.email = c2.email AND c1.id <> c2.id;