时间:2021-07-01 10:21:17 帮助过:2人阅读
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 | john@example.com |
- | 2 | bob@example.com |
- | 3 | john@example.com |
- +----+------------------+
- 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 | john@example.com |
- | 2 | bob@example.com |
- +----+------------------+
- <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;
- </code>
SQL 删除重复的电子邮箱
标签:select and The solution strong 一个 -- 查询 group