删除重复记录保留最新记录

Question

在 table 我有 2 列，IP 地址和日期。有 ip 地址重复值。但是日期是独一无二的。我需要删除所有重复的 IP，留下最新的 IP

Answer 1

假设您没有空值并且已分配主键，请尝试此查询...

  DELETE FROM MyTable
LEFT OUTER JOIN (
   SELECT MIN(RowId) as RowId, ipaddress, date
   FROM MyTable 
   GROUP BY ipaddress, date
) as KeepRows ON
   MyTable.RowId = KeepRows.RowId
WHERE
   KeepRows.RowId IS NULL

根据您的要求编辑...

首先您需要将身份设置为您的 table，使用此设置身份

 ALTER TABLE [tablename] ADD Id INT IDENTITY(1,1)

设置身份后，执行以下查询以删除重复的 IP 地址..

DELETE FROM dbo.DataTime WHERE ColumnID NOT IN (SELECT MIN(ColumnID) _
FROM dbo.DataTime group by (ipaddress))

Answer 2

你可以试试DELETE JOIN如果你用mysql:

delete t1
from yourtable t1
join yourtable t2
on t1.ip = t1.ip
and t1.`date` < t2.`date`

Answer 3

试试这个

delete  
from yourtable  aa
where
ROWID in 
(
Select ROWID
from
 yourtable  bb
where aa.ip = bb.ip
and aa.date > bb.date
)

Answer 4

您想删除所有存在较新条目（即具有相同 IP 地址和较早日期的条目）的记录：

delete from mytable
where exists
(
  select *
  from mytable newer
  where newer.ipaddress = mytable.ipaddress
    and newer.date > mytable.date
);

Answer 5

此查询向您展示了一种为 ip 选择除最新行以外的所有行的方法：

WITH 
 --this bit of code just creates some data we can play with because I
--don't have your table structure in my database
 ip_data (ip, creation_date)
 AS
 (SELECT '1.2.3.4',sysdate-1 FROM dual UNION ALL
  SELECT '1.2.3.4',sysdate-2 FROM dual UNION ALL
  SELECT '1.2.3.4',sysdate-3 FROM dual UNION ALL
  SELECT '1.2.3.4',sysdate-4 FROM dual UNION ALL
  SELECT '1.2.3.4',sysdate-5 FROM dual UNION ALL
  SELECT '1.2.3.9',sysdate-1 FROM dual UNION ALL
  SELECT '1.2.3.9',sysdate-2 FROM dual UNION ALL
  SELECT '1.2.3.9',sysdate-3 FROM dual UNION ALL
  SELECT '1.2.3.9',sysdate-4 FROM dual 
  ) 
--this query takes our data with row numbers and excludes any with row number
--1 (that is, the most recent row for each ip)
SELECT
 ip
,creation_date
FROM
  --this query assigns a row number to each row.  The latest row for an ip
  --get row number 1.  Numbering restarts for each ip (PARTITION BY ip)
 (SELECT
   ip  
  ,creation_date
  ,ROW_NUMBER() OVER (PARTITION BY ip ORDER BY creation_date DESC)    rn
  FROM
   ip_data
)
WHERE rn > 1
;

您需要为您的 table 结构修改此内容，但希望评论有意义。一旦你理解了它是如何工作的，你就可以将它放入类似下面的东西中：

DELETE FROM <your table>
WHERE (ip, creation_date) IN
 (<select statement similar to the above>)

删除重复记录保留最新记录

Deleting duplicate records leaving the latest

sql

oracle

sql-delete

试试这个