Solved

SQL selection query question

Posted on 2011-02-27
10
304 Views
Last Modified: 2012-05-11
Hi,

I was wondering if anyone can tell me how to do the following using sql transact for sql server 2008.

I want to select all records in a couple of linked tables where UserId = @UserId AND ThreadId has to be the most recent one and has to be distinct.  

For example user can have many threads but also a lot of messages on the same thread.  On the main page I just want to see the most recent message in that thread plus all the other most recent message in different threads.

Thank you
0
Comment
Question by:Claudiu10
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 6
  • 3
10 Comments
 
LVL 41

Expert Comment

by:Sharath
ID: 34993993
try like this.
select * 
  from (
select *,row_number() over (partition by UserID order by ThreadID desc) rn
  from your_table) t1
 where rn = 1 and UserID = @UserID

Open in new window

0
 
LVL 50

Expert Comment

by:Lowfatspread
ID: 34994009
you need to tell us the structure of your tables and the volumes involved ....

however



select x.Threadid
      ,x.ThreadTopic
      ,x.msgid
      ,x.msgresponse
      ,x.msgtime
      ,x.msguser
  from (select the columns that you want....
              ,row_number() over (partition by t.threadid order by m.msgtime desc) as rn
     -- could be a msg sequence number instead of the msg date and time ... whatever indicates
     -- the latest messages should be in the above order by  xxxxx desc
  from threads as T
 left outer join Messages as M
   on t.threadid=m.threadid
  where t.userid=@userid
    ) as X
 where rn=1
 order by threadid,....

Open in new window

0
 

Author Comment

by:Claudiu10
ID: 35004083
HI,

thanks for the info.  I tried this.  Any idea why it's giving me incorrect column rownum?

SELECT (ow_number() over (PARTITION by t.ThreadId order by m.CreateDate DESC) AS rownum, t.ThreadId, t.ThreadSubject, m.MessageId, m.SentByUserId, m.Body, m.CreateDate, m.MessageTypeId, r.UserId, r.MessageStatusTypeId, r.DateLastModified
      FROM Messages AS m INNER JOIN
MessageThread AS t ON m.ThreadId = t.ThreadId INNER JOIN
            MessageRecipients AS r ON m.MessageId = r.MessageId
                  WHERE rownum = 1 AND r.UserId = @UserId

Thank you
0
Comparison of Amazon Drive, Google Drive, OneDrive

What is Best for Backup: Amazon Drive, Google Drive or MS OneDrive? In this free whitepaper we look at their performance, pricing, and platform availability to help you decide which cloud drive is right for your situation. Download and read the results of our testing for free!

 
LVL 41

Accepted Solution

by:
Sharath earned 500 total points
ID: 35004251
try like this.
SELECT * 
  FROM (SELECT ROW_NUMBER() 
                 OVER(PARTITION BY t.ThreadId ORDER BY m.CreateDate DESC) AS rownum, 
               t.ThreadId, 
               t.ThreadSubject, 
               m.MessageId, 
               m.SentByUserId, 
               m.Body, 
               m.CreateDate, 
               m.MessageTypeId, 
               r.UserId, 
               r.MessageStatusTypeId, 
               r.DateLastModified 
          FROM Messages AS m 
               INNER JOIN MessageThread AS t 
                 ON m.ThreadId = t.ThreadId 
               INNER JOIN MessageRecipients AS r 
                 ON m.MessageId = r.MessageId) t1 
 WHERE rownum = 1 
       AND UserId = @UserId

Open in new window

0
 

Author Closing Comment

by:Claudiu10
ID: 35014115
Thanks for your help.  Appreciate it.
0
 

Author Comment

by:Claudiu10
ID: 35014447
Hi,

Actually there is a problem in my case with this statement.  

I am trying to get all the messages received by a user by the following criteria:

1.  Different thread.
2.  Newest
3.   The user getting the messages can't be the sender.

Problems with this query:

The partitioning does not guarantee that rownum 1 doesn't contain the user reading the messages as the sender.  I don't see a way to put in a where clause in the partition.  Any ideas how I can make that happen?
0
 

Author Comment

by:Claudiu10
ID: 35014454
I also tryed partitioning by senders in a second rownumber but that doesn't guarantee the case where there is more than one thread by the same sender.
0
 

Author Comment

by:Claudiu10
ID: 35014480
sorry think I got it.

added the following in the where clause at the end of the query before the closing bracket.

WHERE m.SentByUserId <> @UserId AND r.UserId = @UserId
0
 
LVL 41

Expert Comment

by:Sharath
ID: 35014492
Are you still looking for any help?
0
 

Author Comment

by:Claudiu10
ID: 35014633
no I got it thanks.  I was making a mistake by putting the where clause after the closing bracket initially.

Thank you
0

Featured Post

Free Tool: Port Scanner

Check which ports are open to the outside world. Helps make sure that your firewall rules are working as intended.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
What is this datetime? 1 33
Enabled trace flag 4135 or 4199 - SQL SERVER 2 34
Estimating my database size 7 51
Adding columns to a table which has non null columns 3 43
Naughty Me. While I was changing the database name from DB1 to DB_PROD1 (yep it's not real database name ^v^), I changed the database name and notified my application fellows that I did it. They turn on the application, and everything is working. A …
Ever needed a SQL 2008 Database replicated/mirrored/log shipped on another server but you can't take the downtime inflicted by initial snapshot or disconnect while T-logs are restored or mirror applied? You can use SQL Server Initialize from Backup…
Are you ready to implement Active Directory best practices without reading 300+ pages? You're in luck. In this webinar hosted by Skyport Systems, you gain insight into Microsoft's latest comprehensive guide, with tips on the best and easiest way…

739 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question