通过登录和注销记录检索在线用户

Question

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如上所述考虑UserLog Table。我将用户的登录或注销操作保存到此表中。如何检索在线用户和登录时间？

Answer 1

这样的事情：

select * from UserLog l1
where Operation = 'Enter' and 
      not exists(select * from UserLog l2 
                 where l1.user = l2.user and 
                       l2.Operation = 'Exit' and 
                       l2.Time > l1.Time)

Answer 2

我认为这应该适合你：

SELECT *
FROM (
    SELECT ROW_NUMBER() OVER (PARTITION BY UL.id ORDER BY UL.Time DESC) AS RN, UL.*
    FROM dbo.UserLog AS UL
    ) AS T
WHERE T.RN = 1
    AND T.Operation = 'Enter';

只需按用户ID对您的表进行分区，然后按上次操作时间排序 - 如果是Enter，那么他必须在线。