ordering by another table column mysql - mysql

Question

I have two tables, messages and thread messages is the main table and thread is where I keep the conversation between two users. I want to select only from messages table and order by thread_id from thread table. I am using the below sql but it doesn't order as I want it.
My aim is when new message is inserted to thread table make the parent message in messages table appear at the top. Does anyone have any idea?
SELECT m.*
FROM messages AS m
JOIN thread AS t
ON t.thread_id = m.id
WHERE ( m.to_user = ?
AND m.deleted != ?
AND m.del2 != ?)
OR
(m.from_user = ?
AND m.conversation = 'true'
AND m.deleted != ?
AND m.del2 != ?)
ORDER BY t.thread_id desc);
messages table
id to_user from_user message is_read deleted del2 conversation
----------------------------------------------------------------------------------------
1 user1 user2 hi mark, true true
2 user3 user4 wass up yo? true true
3 user1 user3 blah blah
thread table
thread_id thread_to_user thread_from_user thread_message thread_message_id thread_is_read
---------------------------------------------------------------------------------------------------
1 user2 user1 hi there, 1 1
2 user1 user2 hey, wassup 1 1
3 user2 user1 not much, hw u doin 1 1
4 user1 user2 doing great and you? 1 0
5 user3 user4 heyyyy 2 1
6 user4 user3 hi, u coming? 2 0
What I am expecting when echoing the row:
id to_user from_user message is_read deleted del2 conversation
----------------------------------------------------------------------------------------
2 user3 user4 wass up yo? true true
1 user1 user2 hi mark, true true
3 user1 user3 blah blah

Answer 1

Try this one:
SELECT DISTINCT(id), to_user,from_user,
message, is_read, conversation
FROM messages
LEFT JOIN (
SELECT thread_id, thread_message_id
FROM messages m
LEFT JOIN thread t
ON m.id = t.thread_message_id
) tbl
ON messages.id = tbl.thread_message_id
ORDER BY tbl.thread_id DESC
See fiddle demo
You could put your WHERE inside the subquery, like:
SELECT DISTINCT(id), to_user,from_user,
message, is_read, conversation
FROM messages
LEFT JOIN (
SELECT thread_id, thread_message_id
FROM messages m
LEFT JOIN thread t
ON m.id = t.thread_message_id
WHERE ( m.to_user = ?
AND m.deleted != ?
AND m.del2 != ?)
OR
(m.from_user = ?
AND m.conversation = true
AND m.deleted != ?
AND m.del2 != ?)
) tbl
ON messages.id = tbl.thread_message_id
ORDER BY tbl.thread_id DESC
See Fiddle Demo with WHERE
Update (Using MAX() with subquery)
SELECT id, to_user, from_user, message, is_read, conversation
FROM (
SELECT m.id, max(t.thread_id) thread_id, m.to_user,m.from_user,m.message, m.is_read, m.conversation
FROM messages m
LEFT JOIN thread t on(t.thread_message_id = m.id)
WHERE ( m.to_user = 'user1'
AND m.deleted != true
AND m.del2 != true)
OR
(m.from_user = 'user3'
AND m.conversation = true
AND m.deleted != true
AND m.del2 != true)
GROUP BY m.id
ORDER BY thread_id desc
) tbl
See Other Demo

Answer 2

please refer the below query and the fiddle example
select m.id, max(t.thread_id) thread_id, m.to_user,m.from_user,m.message, m.is_read, m.conversation
from messages m
left join thread t on(t.thread_message_id = m.id)
group by t.thread_message_id
order by thread_id desc;
fiddle example