Question

I have the following tables:

users:
    user_id
    user_name

message:
    message_id
    thread_id
    to_id
    from_id
    title
    message_text
    message_date        
    status

The desired result of the query I run is to list the title of the most recent message from the most recent threads a long with the thread_id and username and to sort the result by date in descending order. I’m only going to be listing about 10 to 20 results at a time most likely.

The SQL query I came up with seems to be doing this so far, but I feel like I have over complicated it and that there may be a more optimal way to write my query.

    SELECT personal_messages.message_id, 
           personal_messages.thread_id, 
           personal_messages.body, 
           users.username
    FROM users, personal_messages
    WHERE message_id IN 
        (SELECT MAX(message_id) from personal_messages GROUP BY thread_id)
    AND users.id IN 
        (SELECT users.id FROM users WHERE users.id = personal_messages.from_id)
    ORDER BY personal_messages.message_date DESC

Also, if anyone knows a way to get the count of all the messages with the same thread_id, that would be awesome!

Any tips would be greatly appreciated!

Answer 1

One of the subselects could be unnecessary

SELECT personal_messages.message_id, personal_messages.thread_id, personal_messages.body, users.username
FROM users INNER JOIN personal_messages ON (users.id = personal_messages.from_id)
WHERE message_id IN (SELECT MAX(message_id) from personal_messages GROUP BY thread_id)
ORDER BY personal_messages.message_date DESC    

Edit: Also, if anyone knows a way to get the count of all the messages with the same thread_id, that would be awesome!

SELECT MAX(message_id), COUNT(message_id) FROM personal_messages GROUP BY thread_id