Question

在表格中我有2列，IP地址和日期。有ip地址重复值。但日期是独一无二的。我需要删除所有重复的IP，留下最新的IP

Answer 1

如果您使用DELETE JOIN：

，则可以尝试mysql

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

Answer 2

此查询显示了一种为ip选择除最新行之外的所有行的方法：

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
;

你需要为你的桌面结构重做这个，但希望这些评论是有意义的。一旦你理解了它的工作原理，你就可以将其融入以下内容：

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

Answer 3

您想要删除存在更新条目的所有记录（即具有相同IP地址和更高日期的条目）：

$delegate.someproperty

删除留下最新记录的重复记录

3 个答案: