显示重复的行

Question

我得到了一个包含名称和IP地址的列表：

ID | Name     | Address
1  | Peter    | 111.222.333
2  | John     | 999.888.333
3  | Hans     | 111.222.333
4  | Kimberly | 555.555.1111

我正试图找到一种方法来使用SQL显示重复的帐户：

Name  | Second account (found by IP)
Peter | Hans

请帮忙，

谢谢。

Answer 1

你只需要将表加入自己。

select
t1.name, t2.name as second_account
from
your_table t1
inner join your_table t2 on t1.address = t2.address and t1.name < t2.name

Answer 2

如果你有两个以上的重复

1  | Peter    | 111.222.333
2  | John     | 111.222.333
3  | Hans     | 111.222.333

fancyPants的查询将返回所有可能的组合，如

Name  | Second account (found by IP)
Peter | Hans
Peter | John
John  | Hans

这将返回重复列表，而不是对：

select address, name
from tab
where address in
  ( select address
    from tab
    group by address
    having count(*) > 1
  )

根据您的需要，这也可能没问题：

select min(name), max(name), count(*) as number_of_duplicates
from tab
group by address
having count(*) > 1