Question

确定SQL Server表中重复记录的最佳方法是什么？

例如，我想查找表格中收到的最后一封重复的电子邮件（表格包含主键，收到的日期和电子邮件字段）。

示例数据：

1  01/01/2008 stuff@stuff.com
2  02/01/2008 stuff@stuff.com
3  01/12/2008 noone@stuff.com

Answer 1

类似这样的事情

select email ,max(receiveddate) as MaxDate
from YourTable
group by email 
having count(email) > 1

Answer 2

尝试类似：

SELECT * FROM (
  SELECT *, 
  ROW_NUMBER() OVER (PARTITION BY ReceivedDate, Email ORDER BY ReceivedDate, Email DESC) AS RowNumber 
  FROM EmailTable
) a
WHERE RowNumber = 1

请参阅http://www.technicaloverload.com/working-with-duplicates-in-sql-server/

Answer 3

您是否无法加入电子邮件字段中的列表，然后查看结果中的空值？

或者更好的是，计算每个电子邮件地址的实例？并且只返回带有计数的＆gt; 1

甚至可以使用电子邮件和ID字段。并返回电子邮件相同的条目，ID不同。（为避免重复，请不要使用！=而是使用＆lt;或＆gt ;.）

Answer 4

试试这个

select * from table a, table b
where a.email = b.email

Answer 5

SELECT [id], [receivedate], [email]
FROM [mytable]
WHERE [email] IN ( SELECT [email]
    FROM [myTable]
    GROUP BY [email]
    HAVING COUNT([email]) > 1 )

Answer 6

你想要最后一项的清单吗？如果是这样，你可以使用：

SELECT [info] FROM [table] t WHERE NOT EXISTS (SELECT * FROM [table] tCheck WHERE t.date > tCheck.date)

如果您想要所有重复电子邮件地址的列表，请使用GROUP BY收集类似数据，然后使用HAVING子句确保数量超过1：

SELECT [info] FROM [table] GROUP BY [email] HAVING Count(*) > 1 DESC

如果您想要最后一个重复的电子邮件（单个结果），您只需添加“TOP 1”和“ORDER BY”：

SELECT TOP 1 [info] FROM [table] GROUP BY [email] HAVING Count(*) > 1 ORDER BY Date DESC

Answer 7

如果您有代理键，则使用SQLMenance帖子中提到的语法相对容易。基本上，由两个或多个行“相同”的所有字段组合。

删除重复记录的伪代码示例。

Create table people (ID(PK), Name, Address, DOB)

Delete from people where id not in (
Select min(ID) from people group by name, address, dob
)

SQL Server重复检查

7 个答案: