sql - 如何选择列值不不同的每一行

Question

我需要运行一个 select 语句，它返回列的值不不同的所有行（例如 EmailAddress）。

例如，如果表格如下所示：

CustomerName     EmailAddress
Aaron            aaron@gmail.com
Christy          aaron@gmail.com
Jason            jason@gmail.com
Eric             eric@gmail.com
John             aaron@gmail.com

我需要查询返回：

Aaron            aaron@gmail.com
Christy          aaron@gmail.com
John             aaron@gmail.com

我已经阅读了很多帖子并尝试了不同的查询，但无济于事。我认为应该工作的查询如下。有人可以提出替代方案或告诉我我的查询可能有什么问题吗？

select EmailAddress, CustomerName from Customers
group by EmailAddress, CustomerName
having COUNT(distinct(EmailAddress)) > 1

score 319 · Accepted Answer

这比以下EXISTS方式快得多：

SELECT [EmailAddress], [CustomerName] FROM [Customers] WHERE [EmailAddress] IN
  (SELECT [EmailAddress] FROM [Customers] GROUP BY [EmailAddress] HAVING COUNT(*) > 1)

score 63 · Accepted Answer

您的查询不正确的是您按电子邮件和姓名进行分组，这形成了一组每个独特的电子邮件和姓名组合在一起，因此

aaron and aaron@gmail.com
christy and aaron@gmail.com
john and aaron@gmail.com

被视为 3 个不同的组，而不是全部属于 1 个单独的组。

请使用下面给出的查询：

select emailaddress,customername from customers where emailaddress in
(select emailaddress from customers group by emailaddress having count(*) > 1)

score 21 · Accepted Answer

21

select CustomerName,count(1) from Customers group by CustomerName having count(1) > 1

于 2013-07-03T06:29:21.263 回答

score 12 · Accepted Answer

How about

SELECT EmailAddress, CustomerName FROM Customers a
WHERE Exists ( SELECT emailAddress FROM customers c WHERE a.customerName != c.customerName AND a.EmailAddress = c.EmailAddress)

score 9 · Accepted Answer

只是为了好玩，这是另一种方式：

;with counts as (
    select CustomerName, EmailAddress,
      count(*) over (partition by EmailAddress) as num
    from Customers
)
select CustomerName, EmailAddress
from counts
where num > 1

score 4 · Accepted Answer

而不是在 where 条件下使用子查询，这会增加大量记录的查询时间。

我建议使用 Inner Join 作为解决此问题的更好选择。

考虑到同一张表，这可能会给出结果

SELECT EmailAddress, CustomerName FROM Customers as a 
Inner Join Customers as b on a.CustomerName <> b.CustomerName and a.EmailAddress = b.EmailAddress

为了获得更好的结果，我建议您使用CustomerID表中的任何唯一字段。复制CustomerName是可能的。

score 0 · Accepted Answer

SELECT        Title, Id
FROM            dbo.TblNews
WHERE        (Title IN
      (SELECT  Title 
FROM dbo.TblNews AS TblNews_1
GROUP BY Title
HAVING (COUNT(*) > 1)))
ORDER BY Title

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sql - 如何选择列值不不同的每一行

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