mysql は重複データを削除し、最小 (最大) ID のデータを保持します。

接続する

DELETE p1
FROM
    Person p1,
    Person p2
WHERE
    p1.Email = p2.Email
    AND p1.Id > p2.Id

サブクエリ

DELETE
FROM
    Person
WHERE
    id NOT IN ( SELECT id FROM ( SELECT min( id ) AS id FROM Person GROUP BY email ) AS m );

からの抜粋:

https://blog.csdn.net/u013967628/article/details/88076520