列出不同大小写的重复项 SQL 服务器

Question

我对数据库很陌生，我正在尝试获取具有不同大小写值的重复值列表，例如在我的数据库中

id | email
---------------------
1  | first@email.com
2  | First@email.com  
3  | second@mail.com
4  | third@email.com

我可以 select 具有

的重复值

 SELECT count(*) as 'duplicates', lower(email) as 'email'
 FROM   my_table
 GROUP  BY lower(email)
 HAVING count(*) > 1;

这个returns:

duplicates | email
------------------------
2          |  first@email.com

Bu 我也想 return 两个不同大小写的电子邮件，例如：

duplicates | email           | email2
-----------------------------------------
2          | first@email.com | First@email.com

注意：从初始查询中我可以看出重复项不超过 2 个（这可能会使查询更简单）

提前致谢！

编辑：它在 Microsoft SQL Server 2012

Answer 1

我会建议 array_agg() 这样你就可以得到所有的：

SELECT count(*) as duplicates, lower(email) as email,
       ARRAY_AGG(DISTINCT email) as all_emails
FROM my_table
GROUP BY lower(email)
HAVING count(*) > 1;

Here 是一个 db<>fiddle.

在SQL服务器中，可以使用STRING_AGG():

SELECT count(*) as duplicates, lower(email) as email,
       STRING_AGG(email, ',') as all_emails
FROM my_table
GROUP BY lower(email)
HAVING count(*) > 1;

很遗憾，DISTINCT 不受支持。

Answer 2

如果您提前知道您的副本不超过两个，您可以很容易地做到：

select Min(email) Email, Max(email) Email2
from t
group by lower(email)
having Count(*)=2

列出不同大小写的重复项 SQL 服务器

List different case duplicates SQL Server

sql

sql-server

case-sensitive

duplicates