Question

I have a database where I keep mail conversations

table "conversations"
ID    SUBJECT
1     meeting on Friday

table "conversations_mails"
ID    CONVERSATION_ID    TEXT                               CREATED_ON
1     1                  "What about a meeting on Friday?"  2012-08-05 10:00:00
2     1                  "that's a good idea!"              2012-08-10 15:00:00

Now, i want to display a conversation overview page, showing a truncated text version of the latest reply. eg

"Meeting on Friday"
That's a good ... 

I try to achieve this via GROUP BY. But what I get is the first reply in the table (“What about a meeting on Friday”), instead of the last “That’s a good Idea”.

This is my SQL statement:

SELECT *, MAX(conversations_mails.created_on) As conversation_last_reply,
  MAX(conversations_mails.id) AS maxId
FROM conversations 
LEFT JOIN conversations_mails ON conversations_mails.conversation_id = conversations.id 
GROUP BY conversations.id 
ORDER BY conversation_last_reply DESC

I know how to get the highest ID via MAX(), but what about the corresponding TEXT entry?

Thank you!

Answer 1

Try this-

SELECT *, MAX(conversations_mails.created_on) As conversation_last_reply,
  MAX(conversations_mails.id) AS maxId
FROM conversations 
LEFT JOIN conversations_mails ON conversations_mails.conversation_id = conversations.id 
WHERE conversations_mails.id = (select max(conversations_mails.id) from conversations_mails where conversations_mails.conversation_id = conversations.id)
GROUP BY conversations.id 
ORDER BY conversation_last_reply DESC