從登錄日誌中獲取最新的IP地址

Question

我在網站上有一個活動日誌表。每個登錄都有日期/時間，用戶ID和IP地址列。

我想檢索一個唯一用戶名列表和最近登錄的IP地址。

什麼是在SQL Server上使用t-sql從表中檢索此最佳方法？

Answer 1

一種便攜式的做法是：

select l.userID, l.Date, l.IpAddress 
from (
    select userID, max(Date) as MaxDate 
    from Log 
    group by userID 
) lm 
inner join Log l on lm.userID = l.userID 
    and lm.MaxDate = l.Date 

如果您有SQL Server的2005+，你也可以這樣做：

select * from 
(
    select userID, Date, IpAddress, 
     Rank() over (Partition BY userID order by Date DESC) as Rank 
    from Log 
) tmp 
where Rank = 1 

Answer 2

我猜在這裏一些列/表名，和我「M假設用戶名來自一個表（和你不存儲每個時間日誌中的用戶名）：

;WITH x AS 
(
    SELECT userID, IPaddress, rn = ROW_NUMBER() OVER 
    (PARTITION BY UserID ORDER BY datetimecolumn DESC) 
    FROM dbo.LogTable 
) 
SELECT u.username, x.IPAddress 
FROM x INNER JOIN dbo.Users AS u 
ON u.userID = x.userID 
WHERE x.rn = 1; 

Answer 3

select distinct(user_name), (select top 1 IP_address from log_table where user_name=LOG.user_name order by log_date desc) 
from log_table LOG