Question

HI Guys

我有一张像下面这样的表

SurveyID(uniqueidentifier) PKey,UserID(uniqueidentifier),Time(DateTime)

我可以为UserID复制，Time是当我们向表中插入记录时的当前时间。

我必须为每个用户选择最后插入的recrod。

我的所有查询都失败了。对此有何帮助？

由于图图

Answer 1

SELECT u1.*
FROM Users u1
WHERE NOT EXISTS 
    (SELECT *
     FROM Users u2
     WHERE u1.ID = u2.ID AND u2.Date > u1.Date)

Answer 2

WITH rows AS (
    SELECT 
        ROW_NUMBER() OVER (PARTITION BY UserID ORDER BY [Time] DESC) AS __ROW,
        SurveyID,
        PKey,
        UserID
    FROM yourTable
)
SELECT SurveyID, PKey, UserID
FROM rows
WHERE __ROW = 1;

这适用于Oracle和SQL Server。关于MySQL或Postgres不确定。它在Access中不起作用。双下划线__ROW只是我有时会使用的命名约定。

Answer 3

select * from
(
select *, row_number() over(partition by userid order by time desc) as sno from users
) as t
where sno=1

Answer 4

SELECT * 来自用户在哪里时间IN （SELECT max（时间）来自用户 GROUP BY USERID）

Group BY子句的问题

4 个答案: