Question

I’ve a Table as below

ID  |FromId |ToId   |Message|DateTime
------------------------------------------
1   |1      |2      |a      |15:00
2   |1      |2      |b      |15:01
3   |1      |2      |c      |15:02
4   |2      |1      |d      |15:03
5   |3      |1      |e      |15:04
6   |3      |1      |f      |15:05
7   |1      |3      |g      |15:06

what I want to get is Every last message of Peers.

For example: User 1 and user 2 has 4 messages (ID:1,2,3,4) and user 1 and user 3 has 3 messages (ID:5,6,7)

I want to get only latest Message record from users, I need a SQL query which will give the result like this:

*sql code here ? -- I need this.

result (for: where UserID=1) :

ID  |FromId |ToId   |Message|DateTime
------------------------------------------
4   |2      |1      |d      |15:03
7   |1      |3      |g      |15:06

Any Ideas ? I’ve tried with Distinct etc. but it didn’t worked somehow. Please help.

Sorry Guys I guess I forgot to mention that I need the latest record from Peer, not the latest record from one user, for example for user 1 and user 2 I need the latest record from them, no mather which one is From or which one is To.. I need the latest record from both which is ID 4 in our case no other records.

Answer 1

If Sql Server 2005+, you might use row_number() over ( … ) to group, order and number records, and then retrieve only the ones being first in their group:

; with cte as
(
  select *,
      -- Group by user not being searched for
         row_number() over (partition by case when FromID = @UserID
                                              then ToID
                                              else FromID
                                          end
      -- Last date will be numbered as 1
                            order by [DateTime] desc
                           ) rn
    from Table1
-- Filter only messages sent from or received by certain user
   where (FromID = @UserID or ToID = @UserID)
)
select *
  from cte
-- Get last dates only
 where rn = 1