SQL 删除重复的电子邮箱

Posted 2021-02-13 sumelt

编写一个 SQL 查询，来删除 Person 表中所有重复的电子邮箱，重复的邮箱里只保留 Id 最小 的那个。

+----+------------------+
| Id | Email            |
+----+------------------+
| 1  | [email protected] |
| 2  | [email protected]  |
| 3  | [email protected] |
+----+------------------+
Id 是这个表的主键。

例如，在运行你的查询语句之后，上面的 Person 表应返回以下几行:

+----+------------------+
| Id | Email            |
+----+------------------+
| 1  | [email protected] |
| 2  | [email protected]  |
+----+------------------+

Solution Code

delete 
from Person 
where Id not in
(
    select p.min
    from
    (
        select min(Id) as min 
        from Person 
        group by Email
    ) as p
)

-- other ways
delete p1 from person p1, person p2
where p1.email = p2.email and p1.id > p2.id;