need assistance with sql query

in my web application, I have a feature where users can message one another. In their "inbox", I currently have a list of all of their message records displayed in the following format:

FROM            SUBJECT                                             DATE
User A           re: subject for msg1                       10-9-2015
User B           re: subject for msg1                       10-8-2015
User A           re: subject for msg1                       10-7-2015
User B           re: subject for msg1                       10-6-2015
User A           re: subject for msg2                       10-9-2015
User C           re: subject for msg2                       10-7-2015
User A           re: subject for msg2                       10-4-2015
User C           re: subject for msg2                       10-1-2015


Instead of having each message displayed in my table, I want to just have one version of each message, similar to how gMail displays messages. so it would look like:

User B           re: subject for msg1                       10-9-2015
User A           re: subject for msg2                       10-9-2015

the latest version would be what displays. For my table structure, I have a table named tblMessages that contains a messageID column, which is unique to that message, as well as a conversationID column, which is how I group messages between two users together. Right now the following query gives me ALL messages for one user:

select id = messageID, 
         starred = case starred when 1 then 'starred' else 'not starred' end, 
         [from] = displayName, 
         subject = msgSubject,
         [date] = sentDate, 
         beenRead = case beenRead when 1 then '1' else '0' end 
from tblMessages m 
         inner join tblUsers u on m.msgFrom = u.userID and u.status = 1 
where msgTo = 100 and 
        to_deleteDate is null 
order by sentDate DESC

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how can I tweak it to return the latest message for each conversation?
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Big MontySenior Web Developer / CEO of ExchangeTree.org Asked:
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Ryan ChongCommented:
perhaps we can try:
Select a.*
from
(
	select id = messageID, 
		 starred = case starred when 1 then 'starred' else 'not starred' end, 
		 [from] = displayName, 
		 subject = msgSubject,
		 [date] = sentDate, 
		 beenRead = case beenRead when 1 then '1' else '0' end  ,

		row_number() over (partition by messageID order by sentDate desc) idx

	from tblMessages m 
		 inner join tblUsers u on m.msgFrom = u.userID and u.status = 1 
	where msgTo = 100 and 
		to_deleteDate is null 
) a
where a.idx = 1
order by [date] DESC

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Big MontySenior Web Developer / CEO of ExchangeTree.org Author Commented:
thx for such a speedy response, much appreciated!

This mostly worked, I only had to change

row_number() over (partition by messageID order by sentDate desc) idx

to

row_number() over (partition by conversationID order by sentDate desc) idx

to get the data I wanted. Thanks again!
0
Ryan ChongCommented:
coool, glad that could make some helps here cheers
0
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Microsoft SQL Server

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