sqlite3 query by max and filter by second factor

Question

I have:

TABLE MESSAGES
 message_id | conversation_id | from_user | timestamp  |  message

I want:

1. SELECT * WHERE from_user &l         


        

Answer 1

Try below sql to achieve your purpose by group by twice.

select m.*
from
Messages m
-- 3. and then joining to get wanted output columns
inner join
(
    --2. then selecting from this max timestamp - and removing duplicates
    select conversation_id, max(timestamp), message_id
    from
    (
        -- 1. first select max message_id in remainings after the removal of duplicates from mix of cv_id & timestamp
        select conversation_id, timestamp, max(message_id) message_id
        from Messages
        where message <> 'me'
        group by conversation_id, timestamp
    ) max_mid
    group by conversation_id
) max_mid_ts on max_mid_ts.message_id = m.message_id
order by m.message_id;

http://goo.gl/MyZjyU