Question

This is my table struct in sql server 2008:

+--------+-----+---------------------+
|  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 |
+--------+-----+---------------------+

This record in the table are updated by other application every 30 seconds.

Now,I want to query the latest records of all the user in the table.

Any way to implement it using just one sql query?

Answer 1

This will list the user and the latest time entry

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

If you need the associated data, try this

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