Question

这是我在sql server 2008中的表结构：

+--------+-----+---------------------+
|  user  | val |        time         |
+--------+-----+---------------------+
|     kk |  21 | 2011-12-12 12:23:00 |
|     dd |  33 | 2011-12-12 12:23:00 |
|     kk |  22 | 2011-12-12 12:23:30 |
|     dd |  33 | 2011-12-12 12:23:30 |
+--------+-----+---------------------+

表中的此记录每30秒由其他应用程序更新。

现在，我想查询表中所有用户的最新记录。

使用一个SQL查询实现它的任何方法吗？

Answer 1

这将列出用户和最新时间条目

select user,max(time)
from table
group by user

如果您需要相关数据，请尝试此

select a.* 
from table a
join ( select user,max(time) as TheLatest
       from table
       group by user ) xx
on a.time=xx.theLatest and xx.user=a.user

Answer 2

SELECT * FROM
(
    SELECT

            USER
            ,Val
            ,ROW_NUMBER() OVER (PARTITION BY User,Time ORDER BY Time DESC) AS SlNo
    FROM    myTable
) result
WHERE       SlNo = 1

Answer 3

尝试这个

DECLARE @tbl table(ID INT,dtm datetime)

    insert into @tbl 
    values  (1,'2011-09-14 00:59:00'),
            (2,'2011-09-15'),
            (2,'2011-09-15 05:10:00'),
            (5,'2011-09-16 05:10:00'),
            (8,'2011-10-29 05:10:00'),
            (5,'2011-10-29'),
            (6,'2011-10-30')


    select MAX(dtm),ID from @tbl 
       GROUP BY  ID

寻找一个SQL查询字

3 个答案: